The boss of a leading economic think tank has said that the “black hole” in the UK’s public finances is equivalent to the Conservative Party’s pre-election National Insurance cuts.

Former chancellor Jeremy Hunt cut National Insurance by 2p in the last spring budget before the election, after making the exact same cut in the autumn statement last year.

The combined cuts were expected to save the average earner £900 a year.

At the time, Hunt argued that it would make the tax system fairer and help revive the economy.

In order to pay for the tax reductions, the former government insisted it was looking at further public spending cuts, to be introduced if the Conservatives had won the recent election.

Paul Johnson, director of the Institute for Fiscal Studies, said on Monday that it was “striking” that £20 billion “black hole” is of the same scale as Hunt’s NI cuts.

Johnson told BBC Breakfast: “It is very striking that if this problem is about £20 billion big that is exactly the scale of the National Insurance cuts implemented by Jeremy Hunt just before the election.

“Now, if those cuts were implemented in the knowledge that there was this kind of hole that is not good policy to put it mildly.”