Aircraft carriers: NAO fear over defence review change
The National Audit Office has expressed deep concern about changes to the Royal Navy's two new aircraft carriers made in the 2010 defence review.
The NAO queried whether the changes represent value for money and pointed out there would be a decade-long gap without aircraft carrier capability.
Margaret Hodge, chairman of the Commons Public Accounts Committee, said the report was "deeply worrying".
Defence Secretary Liam Fox said changes put the programme "back on track".
In its report, the NAO said changes to the carrier programme in the government's strategic defence and security review (SDSR) had created "significant levels of operational, technical, cost and schedule uncertainty", with the final total cost of the programme now set to exceed £10bn.
The ships - HMS Queen Elizabeth and HMS Prince of Wales - were saved from defence cuts under the coalition government because it said it would cost more to cancel the projects than proceed with them.
Ministers agreed to change the design of one, or both, of the aircraft carriers to make them compatible with the US Navy's version of the Joint Strike Fighter.
HMS Prince of Wales will not enter service - it will be built but not kitted out, and then kept as a reserve vessel - while HMS Queen Elizabeth is expected to go into service around 2020, with both said to cost some £6bn.
The NAO said the decision to buy a different version of the aircraft has delayed the entry into service date by two years, leaving the UK without a carrier able to launch aircraft for a decade and adding significant new risks to the project.
The Whitehall spending watchdog pointed out the decision to make only one carrier with aircraft operational means the UK will only have a carrier at sea for between 150 and 200 days per year - meaning it will rely heavily on allies to fill the gap.
Ms Hodge said the report also revealed that cancellation of the aircraft carriers had been feasible.
She said the report showed cancelling one carrier would save £200m in the long term and cancelling both would save £1.2bn over the same period.
Ms Hodge told the BBC: "It's a very depressing report. This is a project that has been plagued with poor decision-making.
"What the government decided to do in the defence review was substantially change the design and buy a different plane.
"What the report says is that it's something technically which has never been achieved elsewhere in the world and that we have no idea of the costs.
"What we are getting is a delay without a capability for a decade of a carrier on the seas.
"The costs haven't been cut, they've been delayed by delaying the purchase of the plane, by mothballing one of the carriers."
But BBC defence correspondent Caroline Wyatt said the MoD's own list of options contained in the report showed that would have meant accepting the demise of the UK's shipbuilding industry.
Dr Fox insisted that decisions made in the defence review had cut the overall costs by more than £3bn.
He said: "We inherited a complete mess from Labour, a carrier programme which they didn't have the money for in the budget, where they had the wrong design on the ship, and the wrong planes to go on it.
"So we inherited a starting point that we would not have chosen, but having said that, we had to take the appropriate decisions to make it inter-operable with the United States and to give us 50 years of the best utility we could have in terms of power projection."
Last November, the UK and France signed a defence treaty that agreed to share aircraft carrier resources by keeping at least one vessel at sea between the two countries at any one time.
Each will be able to use the other's carrier in some form for training and possibly for operations.
The SDSR in October 2010 outlined cuts of £4.7bn over four years.
The new carriers will replace the 22,000-tonne Invincible class aircraft carriers, HMS Invincible, HMS Illustrious and HMS Ark Royal.
HMS Invincible, mothballed in 2005, was put up for sale on a government internet auction website, while Ark Royal - the navy's flagship - was decommissioned in January and HMS Illustrious will be decommissioned in 2014.