The Pentagon decision to award EADS, the European defence contractor, and Northrop Grumman a $35bn contract to supply refuelling tankers to the US Air Force came under a barrage of fire on Tuesday as more lawmakers joined the chorus of critics on Capitol Hill.

Harry Reid, the Democratic Senate majority leader, said Congress should hold hearings on the unexpected result. Most analysts had predicted the Air Force would select Boeing, which has supplied the US military with tankers for five decades.