It was one of George Osborne’s most effective soundbites. Before, during and after the 2010 general election, the man who served as David Cameron’s chancellor for six years blamed his austerity measures on Labour’s failure to “fix the roof while the sun was shining”.

What goes around comes around. The Office for Budget Responsibility was set up by Osborne in 2010 to keep tabs on the state of the public finances free from the clutches of politicians and has now published its first report into the long-term fiscal risks facing Britain.

Its message was brutally simple. The UK has had a recession once in every decade since the 1970s and there is a 50% chance of there being another one in the next five years. Recessions play havoc with the public finances: three of those since the 1970s have seen the budget deficit – the difference between what the government spends and its income in any one year – rise to 6% or more.

UK public finances face twin threat from Brexit and downturn, says OBR Read more

“Given their near inevitability, but unpredictable timing, there is little policymakers can do in advance beyond recognising that they will need to accept their fiscal costs at some point in the future,” the report said. “This is one reason why academic research and International Monetary Fund advice says that governments should aim to create fiscal space in normal times.” Creating fiscal space in normal times is just a posh way of saying governments should fix the roof while the sun is shining.

So how is the repair job going? Well, the good news is that the deficit is now running at only a quarter of its 10% peak. The bad news is that the ratio of national debt to national income – the accumulation of all the deficits racked up down the years – has doubled since the start of the crisis. The roof has not been fixed at a time when both short-term and long-term pressures are building.

In the short term, Theresa May’s government eased up on the deficit reduction plan inherited from Cameron and saw the result of the election as evidence of “austerity” fatigue. The cost of the overnment’s survival – a £1bn package of financial support for Northern Ireland – has led to demands for higher spending in other areas, most notably public sector pay.

Longer term, the population is getting older, which means that health care costs are inevitably going to rise. That needs to be taken into account when the government is making its fiscal plans.

So does the impact of Brexit. While the OBR’s report was careful to make no assessment of the cost of leaving the EU, it did stress how sensitive the public finances were to even quite modest changes in the economy’s long-term economic performance. Should the economy’s long-term trend growth rate fall by 0.1 percentage point as a result of weaker trade and investment following departure from the EU, there would be a slow-burn effect on the public finances. Over 50 years, the cumulative impact of weaker growth and lower tax receipts would lead to the debt to GDP ratio being 50 percentage points higher.

Even before Brexit, the OBR had been forced to reassess some of its key assumptions by virtue of the economy’s failure to bounce back from the financial crisis and the deep slump of 2007-09. For many years it kept predicting that productivity growth would recover to its long-term trend of 2.2%. But this estimate was cut twice in 2016 – first to 2% and then to 1.8%.

It is always tempting, the OBR notes, for a government to indulge in a few tax and spending giveaways on the basis that the money will be clawed back by takeaways tomorrow. “The risk there, of course, is that tomorrow never comes.”