LONDON May 10 (Reuters) - Britain said it was to buy vertical take-off fighter jets for its future aircraft carriers, a policy shift on a key weapons purchase that risks being seen as another government gaffe and further evidence of defence mismanagement.
Britain said on Thursday it will buy the F-35B variant of the Lockheed Martin-built Joint Strike Fighter, the model David Cameron said was too expensive, following a defence review after he became prime minister in 2010.
That review, criticised by many as being rushed, set the course for defence for five years. A key move was to order the F-35C, which requires catapult and arrester wires, or "cats and traps", on one of Britain's two new aircraft carriers to help the fighters take off and land.
The cost of the system has doubled to 2 billion pounds ($3.2 billion) since first estimates, the defence ministry (MoD) said.
The F-35B does not need cats and traps. The cash cost savings have an operational price - a reduced range and smaller weapons payload than the F-35C.
Also, cats and traps would have delayed carrier strike capability by three years to 2023, the MoD said, adding it had spent 40 million pounds on the system.
"This government will not blindly pursue projects and ignore cost growth and delays," defence secretary Philip Hammond said.
Cameron told parliament two years ago cats and traps were necessary to "allow our allies to operate from our operational carrier and it will allow us to buy the carrier version of the JSF which is more capable, less expensive, has a longer range and carries more weapons."
Reverting to the F-35B planned by the previous Labour government will likely be embarrassing for Cameron.
The switch came at a bad time for the government, which has lurched from one blunder to another in recent weeks, and is also difficult for the MoD, which watchdogs have criticised over botched procurement programmes.
Senior defence officials said facts had changed since 2010, and Britain's allies were "completely relaxed" about the diminished interoperability of Britain's planned carriers.
Senior defence officials also said the F-35B would give Britain the option to use its two new aircraft carriers.
"It demonstrates what a terribly bad exercise the SDSR was," said Eric Grove, defence analyst at the University of Salford, referring to the 2010 Strategic Defence and Security Review.
Lockheed is developing the multirole stealth F-35 for the U.S. military and eight international partners at a projected cost of around $396 billion.
Britain committed in 2001 to buy 138 of the aircraft, mostly the F-35A conventional fighter, to replace Harrier and Tornado jets. In 2010, the current government said it would cut the number of F-35s.
The MoD said it would not make a decision on the number of JSFs it will order before the next defence review in 2015.
British group BAE Systems is a key contractor on the project. Other British contractors named by Lockheed include Cobham, Rolls-Royce, Ultra Electronics, and Martin-Baker Aircraft Company.