By Caroline Wyatt
Defence correspondent, BBC News
As many as 10,000 jobs in the UK are connected to the carrier project
Delays of between one and two years to the in-service date of the UK's two new aircraft carriers have been announced by Defence Secretary John Hutton.
The £4bn carrier project is one of the biggest items in the Ministry of Defence equipment programme.
The programme has been reviewed by ministers, looking for savings.
The announcement came in a written ministerial statement on Thursday afternoon.
Britain's two new aircraft carriers, HMS Queen Elizabeth and HMS Prince of Wales, were due to come into service in 2014 and 2016, as the biggest and most powerful warships the UK has ever built.
However, the timetable has fallen victim to an MoD budget under severe strain, with its procurement plans outstripping the cash available.
Cancelling major programmes was not seen as an option by the MoD: Too many jobs are at stake - up to 10,000 related to the carrier project alone, many of them in key constituencies.
So the projects are being delayed instead, in an effort to balance the books.
With the construction of the joint strike-fighter aircraft that will fly from the warships already running late, the MoD argues that it makes sense to put off the completion of the carriers themselves and slow down the work.
However, Mr Hutton's willingness to delay this key programme only underlines the severity of the cash crisis facing the MoD.
He has said in the past that he wants his department to "live within its means", while prioritising support for front-line forces in Iraq and Afghanistan.
On a practical level, the delay means that the Royal Navy will have to put off the retirement of HMS Illustrious and HMS Ark Royal, the existing carriers.
Illustrious, the flagship of the fleet, has been in service since 1982 and is due to be retired in 2012. Ark Royal entered service in 1985 and is due to go out of service in 2015.
Retired Rear Admiral Scott Lidbetter says keeping the current aircraft carriers going should be possible.
"We can run on the existing Illustrious-class aircraft carriers. If the delay is one to two years, that is achievable and it wouldn't be the first time we've extended the life of ships."
However, critics say delays will make the new aircraft carriers more costly in the long-run.
"It's bad for confidence in industry as we don't know which jobs will be safe and which will not.
"The delay means the new carriers are likely to be more expensive in future than today, and that means higher bills for the taxpayer later on," Liam Fox, the shadow defence secretary, told the BBC.
The Army will suffer its own further delays to its long-awaited FRES family of utility vehicles, with the project now being "restructured", although the use of urgent operational requirements or UORs has meant that £700m is already being spent on new armoured vehicles for front-line use, mainly in Afghanistan.
The good news for the armed forces was an increase in the number of helicopters and hours available to commanders in Afghanistan.
Mr Hutton announced an extra £70m from the Treasury Reserve to upgrade 12 Lynx Mark 9 helicopters with new engines, with the first aircraft available by the end of 2009.
He also said Britain's Merlin helicopters would be moved to Afghanistan once they had completed their mission in Iraq next year.
Critics, however, say all this simply puts off the real issue - that Britain's defence budget remains in turbulent waters, with more projects on its books than it can afford in the long run, with the warning that tough, perhaps unpopular decisions can't be put off forever.
HMS QUEEN ELIZABETH AND HMS PRINCE OF WALES
Displacement: 65,000 tonnes
Length: 280m (920ft)
Width (at flight-deck level): 70m (230ft)
Keel to masthead: 56m (184ft)
Nine decks (plus flight deck)
Speed: 25+ knots
Range: 8,000-10,000 miles
Aircraft: 36 F-35 Joint Strike Fighters and four Airborne Early Warning aircraft, plus EH 101 Merlin helicopters
Crew: 1,450 (including air crew)
Weapons: Phalanx close-in weapon systems; 30mm and mini-guns
Source: Ministry of Defence