LONDON, Sept 28 Reuters Britain39;s Institute for Fiscal Studies IFS estimated on Thursday that there was a 90 chance that public borrowing in four years39; time would be higher than the government39;s budget watchdog has forecast.

The IFS a nonpartisan think tank closely watched by politicians and economists said borrowing in the 202728 tax year was likely to be 40 billion pounds 49 billion higher than the Office for Budget Responsibility OBR forecast in March, at 3.1 of gross domestic product rather than 1.7.

Finance minister Jeremy Hunt will set out new OBR forecasts and budget plans on Nov. 22, when he will seek to reconcile lowering inflation with fellow Conservative lawmakers39; desire for tax cuts ahead of a national election expected next year.

Borrowing in the 202223 financial year totalled 128 billion pounds, or 5.1 of GDP, as Britain39;s government spent heavily on energy subsidies after Russia39;s invasion of Ukraine pushed up households39; and businesses39; heating bills.

The IFS said OBR forecasts were unable to adjust for the tendency of British governments to borrow more during unexpected shocks such as the COVID19 pandemic, but to spend the benefits of any unexpected tax windfall.

Past experience suggests that Chancellors don39;t respond symmetrically to economic shocks. This represents a nontrivial risk to the accuracy of official borrowing forecasts, and potentially to fiscal sustainability, IFS economist Isabel Stockton said.

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