The President, known as Ike, met the extra terrestrials at a remote air base in New Mexico in 1954 after FBI officials made contact through “telepathic ­messages”, according to Timothy Good.

Mr Good, who worked for the Pentagon and Congress, said there were “many witnesses” to the encounters at Holloman Air Force base.

Speaking on Frank Skinner’s BBC2 show Opinionated, he said aliens at the first meeting were “Nordic” in appearance, but a deal was signed with a race called “Alien Greys”.

Mr Good said: “Aliens have made both formal and informal contact with thousands of people throughout the world from all walks of life.”

Conspiracy theorists have circulated rumours that the meeting between Eisenhower and aliens took place. But the claims from Mr Good are the first to be made publicly by an academic. Mr Good also said governments around the world have been in contact with aliens for decades.