Public expenditure is set to jump by £3bn more than planned next year as a result of Tuesday’s inflation figures, which will push up the cost of several state benefits.

The basic state pension will rise by £4.55 a week for a single person to £95.25 from next April as a result of the 5 per cent rise in the retail prices index. But an even bigger jump of 6.3 per cent in the so-called Rossi index – used to update unemployment, housing and other income related benefits – is set to add even more to public spending at a time when the economy is slowing. The cost of providing benefits is rising at a time when more people are starting to claim.