Paul Hellyer, a former Canadian Minister of Defencem, said an unnamed former Canadian Chief of Emergency Measures revealed the astonishing story just before his death from a neurological illness.
Mr Hellyer, 92, revealed the claim to a panel of the world's top UFO and alien investigators and experts.
Speaking at the "Hearing on ET Disclosure” in Brantford, Ontario, Canada, Mr Hellyer explained that if he wanted to know about the workings of an alien space craft he would "ask the current chief of emergency measures".
Mr Hellyer, who became a UFO expert after claiming to have seen proof of alien visitations while in office, said: "The reason I know is I interviewed the previous one, who is now deceased, and he went Langley and the CIA asked if he would like to see one of these crafts.
Conspiracy theorists have insisted for years Area 51 is where evidence of alien visitations of Earth are secretly held away from public view, including the remains of the alleged 1947 Roswell flying saucer crash.
The top-secret military base in the Nevada desert, America, has intrigued and mystified UFO and alien chasers for years, particularly as the US Government only and reluctantly confirmed its existence in 2013.
Mr Hellyer added: "I guess, presumably, it was to be in better to cops with it if one crashed here and he was involved in trying to do something positive about it.
"But before he was allowed to go had to go he had to sign an oath of secrecy and not tell anyone, and during his life he didn't tell anyone including his wife, and an Air Force buddy phoned me and he was dying of
Lou Gehrig’s disease and at that point he felt he should tell someone. They flew him to Area 51 and let him go inside one and observe it and make notes and this sort of thing.
Hellyer said the dying official confirmed he was shown inside alien technology at Area 51.
"I phoned him and he gave me a full report of what he saw and the whole idea of the inside of the craft and this sort of thing, and the fact he had been in a brief and many things, but now he felt he could tell somebody and he thought that would be a good one to tell."
Mr Hellyer was Canadian Minister of Defence from 1963 to 1968 and was deputy prime minister in 1969, but outed himself as a UFO believer 11 years ago.
Last year he made headlines across the globe after claiming up to 80 different species of aliens were in communication with world leaders, but governments across the world were involved in a mass cover up.
He told a TV news interview that some of the aliens lived on one of Saturn's moons called Andromedia.
But sceptics claim he was deluded and to have debunked him because none of Saturn's 62 moons and satellites have this name.
Victor Viggiani, who chaired the hearing, said: "The more important and dramatic piece of evidence presented by Hellyer was a story he told about the day he was called to listen to some death bed confession.
"Paul did not provide dates for the events but he received a call from a man who said that the former head of emergency measures in Canada and that he has a story he wanted to get off his chest."