Liam Fox jet fighter error costs UK millions

David Cameron will rubber stamp an embarrassing U-turn over the Government's £5.2bn super aircraft carrier programme this week to avoid "a floating white elephant".

Defence Secretary Philip Hammond has been warned by officials that his predecessor, Liam Fox, made a massive mistake when he decided to change the jets that should be used on the new carriers.

Mr Fox switched from Lockheed Martin's F35 B class to its supposedly cheaper C variant, a move that was criticised because the planes were not going to be ready until a few years after the ships were launched. The new planes also required changes to the carrier design, costing up to £2bn – with the first ship too far developed to make the changes possible.

Mr Hammond will advise that the Government must switch back to the more conventional B-class jets, which are still expected to cost around $10bn, and has pencilled in an announcement for one week tomorrow.

It is believed that £30m has been spent on designs to accommodate the C class. Labour's defence spokesman Jim Murphy said: "The carrier programme is one of Britain's most strategically important defence projects and yet it is in disarray. More and more people will wonder whether this government can be trusted with the major projects on which our defences rely."

An MoD spokeswoman said: "We are currently finalising the 2012/13 budget and balancing the equipment plan."