Stanton Friedman,a nuclear physicist, is convinced there have been multiple visitations of Earth by aliens, who will ultimately quarantine us here on Earth.
The Canadian claimed there "was not a shadow of a doubt" the existence of intelligent aliens was being covered up by global governments as part of a so-called truth embargo.
Mr Friedman, 82, is a top Ufologist, who has been at the heart of investigations into the mysterious Roswell alleged UFO crash of 1947, after previously working on classified projects for American aerospace corporation McDonnell Douglas.
Speaking to Dailystar.co.uk, he said: "We have enough to prove without a shadow of a doubt that planet Earth is being visited [by aliens].
"This is kept from people because who would want the world in upheaval? There would be mass panic and distress.
"If they (the aliens) want to make themselves known, it's easy – they will."