The whistleblower, who has not been named amid fears he could be accused of breaching the Official Secrets Act, came forward after a recent sighting of what he described as an identical UFO.
The man, now aged in his 70s, came forward after Vanessa Cloete revealed a picture she took of an alleged UFO hovering over the Charnham Park area of Hungerford in Berkshire.
The ex-officer claimed he and a colleague witnessed the same type of object fly down towards them above Greenham Common nuclear missile silos one night in the late 1980s.
Greenham Common, famous for its anti-nuclear protests, was used by the RAF and US Army Air Force, but it closed in 1993 after the Cold War.
The man claims he was made to sign the Official Secrets Act and told never to discuss the event and a US “Men in Black” suited officer swore them to secrecy.
The UFO snapped by Vanessa Cloete last year that caused the whistleblower to break cover
He said: “It looked exactly the same as the photograph in the paper.
“I want the people in Hungerford and Lambourn who saw it to know they’re not alone and that someone believes them.”
Ms Cloete snapped several pictures of the UFO above her home last June.
Other people have since reported sightings of what has become knows as the Hungerford UFO.
But the retired officer is the only ex-offoicial to step forward.
He added: “I was on patrol near the missile silos with a colleague when we tried to fill up with fuel from the pumps.
“They suddenly failed for no apparent reason and then we saw it – just like the photograph, a big, glowing ballbearing with a halo round it.
“It swooped down and my colleague said: ‘What the hell is that?’
“It was just floating above the runway.”
He claimed it sped off at an “impossible speed” and they later informed the control room.
He said next day he was grilled by top brass in the presence of a black-suited American and warned never to mention it.
He added: “It’s been on my mind ever since and the photograph brought it all back.”
regardless of what he saw, the image snapped last year was investigated by the world’s biggest UFO research organisation.
The Mutual UFO Network (MUFON), however, concluded it was likely an out of focus photograph of the planet Venus, which is often seen very bright with the naked eye.
MUFON provided similar examples of strange coloured orbs that were the result of blurred images of Venus.