The grounding of the Tornados would save the air force around £7.5bn, according to a document leaked to The Times, and that would be billions of pounds more than withdrawing the Harrier jet.

The document is part of the Strategic Defence Spending Review, ordered by the Treasury in order to find the cuts.

The decision was mooted at a meeting of the National Security Council at the weekend when it was agreed that one of the three fleets would have to be sacrified.

The fleets consist of the Harrier GR9, the Tornado GR4 and the Eurofighter Typhoon - the latter has been ruled out because it is only just entering service.

Britain presently has just over 200 fast jets.

The MoD has just been told it has to find £20bn to replace the Trident nuclear deterrent.

It had been trying to persuade the Treasury to take it from a general budget but the Treasury insists it has to come out of the defence budget.

The MoD is already committed to a new American-built fighter plane - the F35 - having paid £1bn so far.

It has ordered 138 fighters at a cost of £10bn but this is now expected to be cut.

The selling point for the F35s is that they can penetrate the defences of advanced nations with their stealth capabilities.

However, General Sir David Richards, at present head of the Army but soon to be Chief of the Defence Staff, has argued that wars such as those being conducted in Iraq and Afghanistan are not well served by the use of such aircraft.

The RAF argues that they will act as a deterrent to would-be aggressors.