Labour was accused of a U-turn on defence spending after appearing to backtrack on a key pledge. The Defence Secretary last week there was "no doubt" that the Government would hit the target of 3% of GDP in the next parliament.

But yesterday he would only say that it was an "ambition" to reach that amount by 2034. The Tories seized on the apparent watering down of the pledge ahead of the release of a major military review today which will see Sir Keir Starmer announce plans to build up to 12 new nuclear-powered attack submarines and invest £15 billion in its warhead programme.

Shadow Defence Secretary James Cartlidge said: "All of Labour’s Strategic Defence Review promises will be taken with a pinch of salt unless they can show there will actually be enough money to pay for them.

"Whereas, far from guaranteeing the funding, John Healey has been hung out to dry by Rachel Reeves.

"As recently as Thursday, Healey promised that defence spending would definitely hit 3%, but today he’s completely backtracked.

"These submarines are not due to enter service till the late 2030s, so how can we have any confidence Labour will actually deliver them when they can’t even sustain a policy on defence spending for more than 48 hours?"

Mr Healey appeared to downgrade the 3% promise during an appearance on BBC's Sunday with Laura Kuenssberg show.

He said: "We have a historic commitment to increasing defence spending to 2.5% in two years' time.

"We haven't hit that level since Labour was last in power in 2010. And an ambition to meet 3% in the next Parliament."

A Ministry of Defence spokesman said there had been no change in policy.