Defence chiefs who have been criticised for buying American “Awacs” airborne radar aircraft from Boeing and failing to run an open competition are trying to head off the row by “Anglicising” the aircraft with British-made components.

The RAF wants to replace its worn-out fleet of E-3D “Sentry” aircraft and is understood to be poised to agree a deal with the US aerospace giant for its E-7 “Wedgetail” jets.

However, the E-7 has very little UK content, meaning British companies will hardly benefit from the £2bn deal.

Rival defence companies are furious that the contract has not been opened to competition, though others say the E-7 is already combat proven and other products could take years to develop.