John Healey has backed away from cutting the cost of welfare this parliament, amid dire warnings his first budget could lead to brutal spending cuts because of a £28bn shortfall in public finances.

Experts rounded on Healey’s steady-as-she-goes budget on Thursday, with the Institute for Fiscal Studies saying he had left himself a mountain to climb by ducking big tax and spending decisions.

In a damning analysis, the IFS said Healey would need to have set aside an additional £28bn a year, to offset the impact of inflation on future spending plans and hit the target of spending 3% of GDP in defence by 2030.

Instead Helen Miller, the IFS director, said Healey had opened the way to “a spending review that looks pretty brutal for some departments” – including real-term budget cuts.

“Public service spending plans look extremely tight.…