THE UK Government was called on last night to provide clarity on whether it intends to push ahead with a different kind of jet for Britain's new aircraft carrier after fears rising costs will mean the UK will be without a carrier with jets for more than a decade.

Labour's defence spokesman, Jim Murphy, wrote to Defence Secretary Philip Hammond demanding answers after reports the Ministry of Defence (MoD) is reconsidering its decision.

In last year's defence review the Coalition decided to buy the so-called "cat-and-trap" version of the US joint strike fighter (JSF); this involves a catapult and arrester mechanism.

However, it has now been suggested the MoD might revert to its original decision to buy short take-off and vertical landing jets as redesigning the carrier to take cat-and-trap jets could be too expensive.

According to current plans, HMS Queen Elizabeth, the first carrier, will be mothballed as soon as it is launched in 2016. The second, HMS Prince of Wales, will be put to sea by 2020.

Together, the two carriers, which were to have cost £3.5 billion, are now estimated to cost £6.2bn with MPs saying the price-tag could eventually double to £12bn. They are both being built on the Clyde.

To add to concerns, leaked Pentagon documents suggested there was a design flaw in the new JSF, making it unable to land on aircraft carriers.

The papers said the plane had failed eight simulated landings. Any redesign is likely to prove costly and delay Britain's carrier project for several years.

The MoD is finalising its 2012/13 budget and is "reviewing all programmes, including elements of the carrier strike programme, to validate costs and ensure risks are properly managed".