OBR warning lays bare the next government’s £120bn dilemma

The Office for Budget Responsibility has acquired an unshowy talent for delivering bad news in a voice so measured that Westminster can pretend, for a while, not to hear it. Its latest assessment of the public finances is not quite a siren, but it is close: Britain, the watchdog says, is travelling an “unsustainable” road, and the bill for changing course is now plainly priced.

The headline figure is stark. To stabilise debt at roughly today’s level, the next government after the coming election will need to raise taxes or cut spending by the equivalent of 3.8 per cent of national income, around £120bn in today’s money. That is not a marginal adjustment, nor the sort of tidy “efficiency” drive that Chancellors like to promise in Budget speeches. It is a political and economic decision of the kind that defines a decade.

In the immediate Westminster drama, the OBR’s warning lands on the desk of Andy Burnham, widely cast as prime minister in waiting. Burnham has signalled a more interventionist state, including greater public control of essentials such as water and housing. He has also spoken about easing the squeeze on family finances and has left open the idea of wealth taxes as a route to higher revenues. Yet he has pledged to follow the fiscal rules associated with Rachel Reeves, including the promise that debt must be falling as a share of the economy. The OBR’s point is that the room for manoeuvre is far smaller than politicians are currently implying, and that any deviation from a plan to reduce borrowing accelerates the timetable of risk.

The context is not mysterious. Britain’s debt pile is close to surpassing £3 trillion, around 95 per cent of GDP, a level described by the watchdog as “challenging” both by historical standards and compared with similar countries. That alone would be manageable if demographics were stable and public services cheap. They are not. The OBR’s long-run projections, which are never a forecast but are a map of pressures already in motion, show debt rising relentlessly under the weight of an ageing society, higher health spending and a state pension that grows faster than the economy. Without changes, the debt ratio could approach 300 per cent of GDP within 50 years. In other words, if the state keeps making promises on current terms, it will accumulate obligations that the economy cannot carry without either punishing taxation, a hollowing out of services, or a crisis of confidence in the public finances.

It is the phrase “within a decade” that deserves attention. These are not the sort of warnings designed solely for the distant horizon, where politics can safely file them under “not my problem”. The OBR’s officials have been explicit that while their central projections show debt becoming unsustainable in the 2040s, there are plausible paths to trouble much earlier, even in the 2030s, if borrowing fails to fall as planned or if the economy suffers another major shock. The mechanics are familiar: higher interest costs, weaker growth, an electorate resistant to cuts, and a market that eventually demands a price for taking comfort on trust.

One reason the warning has bite is that Britain has already used up much of the easy political comfort. The tax burden has risen to what the OBR describes as a peacetime high, yet voters are not feeling richer, public services remain strained, and the state’s future commitments are getting larger. The argument for further taxation is no longer simply a matter of ideology, but of arithmetic. The question is what kind of arithmetic, and who is expected to pay.

The OBR offers a blunt truth that jars with fashionable talk of closing gaps through targeted levies on the wealthy. Over the long term, officials argue, tax cannot be the only lever. Continually raising rates and broadening bases creates “ever-increasing economic distortions and costs”. Even where more revenue can be found, the trade-offs intensify. The UK is a service economy that relies on private investment and internationally mobile capital. Raise taxes on capital too aggressively and you risk discouraging investment and encouraging flight, or at the very least discovering that the yield is uncertain. The watchdog even poured cold water on assumptions about capital gains tax as a gold mine, warning that higher taxes on capital could reduce investment and, because capital moves more readily than labour, the take is less reliable than advocates suggest.

For politicians, the temptation is to focus on taxes that appear painless. The stealth raid on earnings has been conducted through frozen thresholds and quiet adjustments that pull more people into higher bands. Yet the OBR warns that a prolonged squeeze of that kind carries its own danger, including the risk of pushing large numbers of people out of work. This is not a moral point, but a fiscal one. A state that leans too hard on wage earners can erode the very tax base it depends upon, while intensifying a sense of unfairness among those who already feel they are paying more for less.

If taxes cannot do all the work, spending becomes the unavoidable second half of the equation. Here Britain runs into its most politically protected promise: the state pension. The OBR notes that abandoning the triple lock, the commitment to increase the pension by the highest of earnings growth, inflation or 2.5 per cent, has the potential to save taxpayers vast sums over time, as much as £160bn a year in today’s money by 2075. Even allowing for the distant horizon of that particular figure, the message is immediate. The triple lock is not a minor policy detail but a structural driver of future spending, and any government that insists it is untouchable is, in effect, insisting that the pain must be found elsewhere.

This is where the politics becomes combustible. The triple lock has been defended as a guarantee of dignity in retirement and a shield against the economic shocks that often hit older voters with particular force. But it is also a policy that locks in higher spending regardless of the economy’s capacity to pay. As the working-age population shrinks relative to retirees, the burden becomes heavier, and the state’s choices narrow. If the promise is maintained in full, it makes the case for deeper restraint in other areas, including services relied upon by younger households, or for tax rises that fall disproportionately on those in work. That is how fiscal policy becomes a generational argument, even if ministers insist they are above such framing.

The OBR sketches an alternative route: phased tightening rather than a single sharp adjustment. One option is to impose roughly £45bn of tax rises and spending cuts every decade from 2031 to stabilise debt. The appeal of this approach is that it spreads the pain and avoids a single, politically fatal Budget. Its weakness is that it demands sustained discipline across multiple parliaments, a trait the modern British state has not shown with much consistency. It also assumes that the country will not face another severe shock that forces emergency borrowing, the very scenario the watchdog warns would bring the crisis forward.

To understand why the OBR is pressing the point now, it helps to recall what makes debt fragile. The UK is not a household and does not “run out of money” in the simple sense. It borrows in its own currency and has a central bank. But debt becomes dangerous when markets lose confidence in a government’s willingness or ability to stabilise it, and when interest costs begin to compound faster than growth. Once that dynamic takes hold, policy choices become more brutal. Taxes must rise faster, spending must fall more quickly, or inflation becomes a tempting, and socially corrosive, escape route. A country can muddle through a long time until, abruptly, it cannot.

In recent years Britain has come to treat fiscal credibility as a kind of mood rather than a metric. It is invoked when useful, ignored when awkward, and defended with slogans about “tough choices” that rarely specify what will actually be cut or taxed. The OBR, in its careful way, is trying to pull the conversation back to specifics. It is also, implicitly, reminding politicians that fiscal rules are not a decorative accessory. If debt is to be falling, a government that promises more public control, higher day-to-day spending, and relief for households must explain how the sums will be reconciled without relying on hopeful growth forecasts.

This is where Burnham’s positioning matters. He has spoken of wealth taxes as a means of raising more revenue. The political logic is obvious: target those with the broadest shoulders, relieve pressure on working families, and signal a break with a model that has often rewarded asset owners over wage earners. Yet the fiscal logic is more complicated. Wealth taxes can raise money, but they are difficult to design, expensive to administer, and vulnerable to avoidance. They can also be unstable as a long-run revenue source if they trigger behavioural change. The OBR’s warning about a “war on wealth” backfiring is not a defence of privilege; it is a reminder that states cannot simply announce that rich people will pay for everything and expect the numbers to add up on a durable basis.

Nor can the Conservative opposition claim to be exempt from this reckoning. Sir Mel Stride, the shadow chancellor, has described the OBR’s message as “crystal clear” and argues for getting spending under control, particularly the welfare bill, while pursuing growth through cutting taxes and red tape, delivering cheaper energy and backing business. The shape of the argument is familiar: discipline on the state, dynamism in the private sector. Yet the tension is equally familiar. Cutting taxes while also stabilising debt requires either cuts to public spending that voters accept, or growth strong enough to lift revenues even at lower rates. Britain has struggled to deliver that growth for much of the past decade and a half, and any party promising both lower taxes and better services is, at best, betting on a rapid reversal of performance.

The welfare bill, too, has become a political shorthand for spending restraint, but it is entangled with health, disability, labour market participation and the fraying of public services. Cutting it is not merely a matter of ministerial will. It requires policy capable of increasing employment and productivity, improving health outcomes, and addressing the structural issues that push people out of work. Otherwise the savings are illusory, achieved through tighter eligibility that can shift costs elsewhere, or through reductions that court a different kind of political crisis.

The deeper problem, which the OBR’s numbers expose without fully debating, is that Britain is attempting to run a European-style welfare state with an American-style aversion to visible taxation. Voters want the NHS protected, the pension guaranteed, schools improved, streets safer, and living standards rising. They also recoil from the idea that funding this requires either broader taxation, such as higher VAT or national insurance, or a frank choice about what the state will no longer do. Politicians, aware of the trap, reach for narrower taxes and optimistic growth assumptions. The OBR is telling them that the trap is closing.

That leaves the country facing a choice that is both technocratic and moral. If taxes must rise, should they rise on income, consumption, property, wealth, or carbon? If spending must fall, should the axe fall on working-age benefits, pensions, public sector pay, investment, or local services? Each option has a distributional effect. Each reshapes incentives and living standards. What the OBR’s warning does is force the recognition that avoiding the argument is itself a decision, one that pushes the problem forward until it arrives as an emergency rather than a policy debate.

There is also a question of timing. The OBR warns that delay makes the eventual remedy more painful. This is not simply because the debt stock grows. It is because demographics worsen and interest costs can rise. Acting earlier allows changes to be phased in, cushioning households and allowing the economy to adapt. Acting later tends to mean abrupt measures in response to pressure, with sharper impacts and less political legitimacy. Britain’s recent experience offers a lesson in how quickly confidence can evaporate when a government appears to be improvising with the public finances.

For Burnham, the practical challenge is to translate the abstract into the credible. If he intends to maintain fiscal rules while expanding public control in key sectors, he must show whether that implies borrowing that is offset elsewhere, investment that pays for itself in productivity gains, or reforms that reduce long-term costs. If he intends to pursue wealth taxes, he must show how they would be designed to raise steady revenue without discouraging investment. If he intends to protect the triple lock, he must explain where the savings will come from instead. These are not questions of political messaging but of national solvency.

Britain still has time to make choices deliberately. That is, in effect, what the watchdog is saying. But the choices are large, and the public mood is not generous to parties that ask for sacrifice without offering a believable return. The OBR’s figures are a kind of mirror held up to a political class that has spent years promising everything at once. They do not dictate a single solution, but they do narrow the space for fantasy. The next government, whoever leads it, will find that the hardest part is not discovering the numbers, but persuading the country that the numbers cannot be wished away.