Britain’s leading tax and spending experts have urged Rachel Reeves to consider announcing billions of pounds in welfare cuts in next month’s budget to help placate jittery financial markets.

After the chancellor gave her strongest hint yet that spending cuts were under consideration, the Institute for Fiscal Studies (IFS) called on Reeves to take “bold” action to plug a potential £22bn shortfall in the government finances.

Warning the chancellor against “doing the bare minimum” to rebuild a financial buffer against her self-imposed fiscal rules, the thinktank said that she could be forced to look again at welfare savings alongside tax rises.

The IFS said options could include scrapping the pensions triple lock, a fresh drive to cut health-related and disability benefits, and limiting growth in spending on special educational needs.

However, such steps could reignite tensions with backbench Labour MPs after ministers were forced into an embarrassing U-turn earlier this year, following an attempt to push through billions of pounds in welfare savings.

Ben Zaranko, an associate director at the IFS, said any changes would need to be presented as reforms which would improve outcomes for individuals. “Trying to do it to chase particular savings isn’t a recipe for success,” he said.

In its annual “green budget” report, which analyses the public finances before Reeves’s speech to the Commons, the IFS said the chancellor could be forced to raise at least £22bn through a mixture of tax and spending measures.

That would restore the £9.9bn of headroom Reeves had left herself at the March spring statement against her main fiscal rule, which requires day-to-day spending to be matched by revenues by the end of the parliament.

The chancellor is expected to face a sharp downgrade from the Office for Budget Responsibility watchdog, thanks to rising borrowing costs, weaker productivity forecasts, and welfare U-turns.

However, the IFS argued there was a strong case for the chancellor to raise significantly more revenue to build a much larger buffer against to avoid the risk of “groundhog day” speculation in future over whether the rules are met.

Helen Miller, the director of the IFS, said: “That wouldn’t be costless – but nor is limping from one forecast to the next under constant speculation that policy will be tightened again. Persistent uncertainty is damaging to the economic outlook.”

In a report prepared alongside Barclays, the IFS said that any measures to raise revenue would need to be seen as “credible” with City investors to avoid rekindling speculation over Labour’s commitment to its fiscal rules.

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Barclays highlighted that a credible attempt to reduce spending, particularly on welfare, would be one way to demonstrate to that the government has the political will and ability to deliver on its fiscal objectives.

Moyeen Islam, a fixed income strategist at the bank, said: “Welfare is totemic. It’s totemic for the market because it shows a willingness to do hard things and burn a little bit of political capital … If you can’t do this with a 150 MP majority, or whatever it is, then when will you do this?

“There would be an appreciation that she is willing to take hard choices. That to me is credibility bolstering or enhancing.”

He said that City investors were fearful that Reeves would take a “Scrabble bag” approach to repairing the public finances, through a combination of small tax-raising measures.

“[If] you cobble together a hodgepodge of measures and they’re not viewed as deliverable or credible, then you are entering into a more adverse market scenario,” he said.

An HM Treasury spokesperson said: “We won’t comment on speculation. The chancellor’s non-negotiable fiscal rules provide the stability needed to help to keep interest rates low while also prioritising investment to support long-term growth.”