By Jonathan Davies

The Conservatives face a £30 billion black hole in their cuts and tax giveaways, according to the Institute of Fiscal Studies (IFS).

The IFS said that even if a Tory government managed to gain £5bn from tax avoidance and cut the welfare bill by £10bn, George Osborne would still need to find an extra £30bn to meet deficit targets and to fund tax giveaways promised in the run-up to the election.

“Despite planning for more austerity, the Conservatives’ detailed tax policies amount to a net giveaway, their detailed social security measures would only provide a 10th of the cuts that they have said they would deliver, and their commitments on aid, the NHS and schools would increase spending in these areas,” the IFS said.

But the IFS also said that Labour had been “considerably more vague about how much they would want to borrow”. It explained that a Labour government would likely borrow around £90bn more than the Conservatives over the next five years.

In its pre-election scrutiny of the party's manifestos, the IFS also said that the Scottish National Party (SNP), which has positioned itself as an 'anti-austerity' party, has plans that are "essentially the same" as Labour and the Conservatives until 2018-19 - the difference being that the SNP would continue to cut after that time.

The Liberal Democrats sit somewhere between Labour and the Conservatives, aiming to cut borrowing by 3.9% of GDP, compared to Labour's 3.6% and the Tories' 5.2%.

Carl Emmerson, the IFS deputy director, said: “There are genuinely big differences between the main parties’ fiscal plans. The electorate has a real choice, although it can at best see only the broad outlines of that choice.”