UFO hunters have been urged to keep an eye on the sky after an expert put the district top of the league for close encounters.

New statistics of unexplained phenomena in the air over Britain have been revealed by the former head of the Government's UFO project, and West Yorkshire is top for sightings with 34 in the last 40 years - many above Bradford.

Nick Pope, who worked for the Ministry of Defence (MoD) investigating UFOs, said the number of sightings in the region could be as many as 1,000, with many going unreported.

He said: "The MoD has received more than 10,000 UFO reports since 1950, so when we say West Yorkshire is the top region, we could be talking about hundreds, if not a thousand.

"While we currently have no explanation why certain places in the UK are alien hot spots, as the research reveals, there are areas where mysterious objects are repeatedly witnessed, so people who want to alien-spot should definitely head to Bradford."

He said one of the most frequent reports is of a triangular aircraft which moves from a virtual stand-still to incredibly high speeds in a matter of seconds.

Others have included groupings of lights and spinning discs, again moving through the night sky at high speeds.

This strange phenomenon has been seen by reliable witnesses, including police officers and members of the air forces, he said.

He said: "When an air force officer tells you that he sees fast jets every day and that he has seen something moving several times faster than the jets, it certainly makes you sit up and take notice.

He added: "I investigated two or three sightings each year to see if I could come up with an explanation. Most turned out to be mis-identified aircraft - I know for a fact that aircraft approaching Leeds Bradford Airport have been mistaken for UFOs - but five per cent still turned out to be unexplained, even after being thoroughly investigated."

Russel Callaghan, editor of Yorkshire-based UFO Data magazine, said his interest started after a close encounter in Odsal in the 1980s.

The former bus conductor said: "Me and my driver got to Odsal Top a little bit early, at about quarter to five in the afternoon. We were stood on a wall overlooking the rugby ground, looking towards East Bierley and were stood having a chat.

"But when we looked up our chins just hit our chests. About 1,000 feet up in the air there was a spinning silver disc. There was no sound and no lights, just the disc spinning very fast. We were looking at it for about seven or eight seconds, then it just shot upwards at tremendous speed."

West Yorkshire was named in first place in yesterday's Virgin Media Files.