Britain's Ministry of Defense had to blank out "uncomplimentary comments" made by officials about members of the public before publishing its UFO files, a newly released document shows.

Following a deluge of requests under the Freedom of Information Act 2000, the Ministry of Defense (MoD) agreed to disclose its full archive of reported sightings of unexplained sights in the skies.

But a previously secret memo reveals that the files had to be edited for references to military technology, relations with other countries and insulting remarks about the public written by defense officials and police.

The document, now posted on the MoD's website, also shows that officials feared publishing only part of the information would "fuel accusations of a 'cover-up'".

Thousands of pages from the department's UFO files have been released through the National Archives since 2008, revealing details of hundreds of reports of strange flying objects and encounters with aliens.