But the release yesterday of secret Ministry of Defence files featuring accounts of strange lights and unexplained objects being spotted in the sky over the UK has fuelled the debate for those who believe such sightings are very real.

The documents, which can be downloaded from the National Archives website, cover the period 1978 to 1987.

Eight files have been released after a Freedom of Information request by UFO researchers. Over the next four years more than 150 files will be thrown open.

Although the files released yesterday concern sightings on mainland UK, local UFO enthusiasts claim Northern Ireland and the Republic have also had their fair share.

"There have been substantial incursions over Northern Ireland," said Lurgan man Miles Johnston, who has made a number of documentaries about UFOs.

"There have been NATO jets tracking objects flying from France the whole way across the Atlantic and the Irish west coast. There have been civil airliners having to be escorted by RAF jets on their way to Dublin Airport because they have had such UFO activity that the UFO's would not allow the aircraft to land — that happened fairly recently. They go back to a very long time ago," Mr Johnston added.

He claims the release of the files is being undertaken by the MoD in order to satisfy public demand for further information on the matter.

"The biggest single request at the MoD is not about the Iraq War or Tony Blair, it is about UFOs," he said.

"What has been going on since the early 1950s is that in order for the scientific community to get a handle on what is going on they have stalled by having various groups and reports to debunk the whole thing.

"There are a number of public spokespeople who will pooh-pooh the whole thing, pour cold water on it, so that the scientific community can get a handle on things, so when the public eventually start demanding answers they have some."

Among the sightings recorded by Ministry of Defence staff were those of alien craft over Wallasey Town Hall and a UFO hovering over Waterloo Bridge.

However, rather than investigating the possibility of visitors from space making a stop at Earth, defence staff have been more interested in checking that UFOs were not in fact covert spying missions by other countries.

Nick Pope, who worked for the MoD for 21 years and was responsible for investigating the sightings, said: "While there's no evidence of little green men in these files, they should be of immense interest to sceptics and believers.

"Most of the UFO sightings here are probably misidentifications of aircraft lights and meteors, but some are more difficult to explain, and include UFOs seen by police officers and pilots, and cases where UFOs have been tracked on radar."