A major U-turn over the fighter aircraft for the Royal Navy's new carriers is expected to be confirmed today.
Ministers are expected to say they have now opted for the jump-jet variant of the US-built F-35 Joint Strike Fighter - as planned by the former Labour government.
The decision - which had been expected before Easter - is believed to have been finally signed off by David Cameron at Tuesday's meeting of the National Security Council.
Under the 2010 Strategic Defence and Security Review, the coalition had planned to switch to the carrier variant - the F-35C - arguing it was a more capable aircraft and, unlike the F-35B jump jet, would be inter-operable with the US and French navies.
However the costs of fitting the necessary catapults and arrester gear - "cats and traps" - to one of the carriers while the other ship was mothballed is reported to have spiralled from an estimated £400 million to almost £2 billion.
In an interview with The Daily Telegraph, Defence Secretary Philip Hammond confirmed that "the facts have changed" on the choice of aircraft since the time of the SDSR.
Nevertheless the decision will be an embarrassment for the Prime Minister who strongly criticised the original decision by Labour to choose the jump jet.
Shadow defence secretary Jim Murphy said the Government's "chaotic" handling of its carrier policy totally undermined its credibility on defence.
"This is a personal humiliation for David Cameron who will to return to Labour's policy, which he previously condemned," he said.
"This is a strategically vital element of the equipment programme on which our security and thousands of jobs depend and yet ministers have treated it with hubristic incompetence, wasting hundreds of millions at a time of painful defence cuts.
"We need a plan to restore Britain's power and prestige at sea, which was so damaged by the discredited defence review, and there are crucial questions on cost and capability ministers must answer."
Hammond will make a statement in the Commons at 11.30am about Britain's carrier strike capability. Murphy will reply for Labour.