Rising costs may force the Ministry of Defence to cut its planned order of 138 stealth jets, officials have suggested for the first time.

MPs on the Commons defence committee heard it was impossible to accurately forecast the costs of the F-35 programme. As costs become clearer as they enter service, the MoD would “make adjustments in our programme accordingly”.

The plan to buy the new jets is the MoD’s second biggest weapons programme, after replacing the nuclear deterrent.

The 2015 Strategic Defence and Security Review declared Britain would “maintain our plan to buy 138 F35 Lightning aircraft” over the coming decades.

The plane is considered the most advanced combat jet ever and will fly from the new aircraft carriers as well as from RAF bases.