The Ministry of Defence plans to open its "X-Files" on UFO sightings to the public for the first time. Officials have not yet decided on a date for the release of the reports, which date back to 1967, but it is hoped to be within weeks.

The move follows the decision by the French national space agency to release its UFO files in March, the first official body in the world to do so.

UFO buffs will be keen to find out what officials knew about some of the UK's most famous sightings and whether any action was taken. One celebrated event - at Rendlesham Forest, Suffolk, in 1980 - has been dubbed "Britain's Roswell" after the UFO incident in the US in 1947. At Rendlesham there were several witness reports of a UFO apparently landing. The released files should support or discount claims that radiation was detected at the site after the event.

David Clarke, a lecturer in journalism at Sheffield Hallam University and author of Flying Saucerers: A Social History of UFOlogy, said opening the MoD's files would make it harder to sustain the idea that evidence for the existence of aliens has been suppressed. "The more of this stuff that they put on their website or put in the national archives, the less it will cost the taxpayer, because at the moment people are writing in about individual incidents and they are having respond," said Dr Clarke, referring to requests under the Freedom of Information Act.

The documents due for release are witness reports of apparent UFO sightings, many by civil pilots and military personnel. Most were simply collected and filed by a small, secret unit within defence intelligence called DI55. A few are thought to have been investigated further by the military, but the details have never been made public. There are 24 files due for release, each containing 200-300 reports of sightings, plus internal MoD briefings and correspondence.