An alien hunter has accused police of withholding facts about a suspected UFO sighting by a helicopter above the Bristol Channel.

Gary Heseltine, editor of UFO Truth magazine, has been investigating the sighting of the invisible object, which was capture by thermal cameras 1000ft over the Bristol Channel.

He has demanded a ‘scientific inquiry’ into the sighting in September 2016.

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Footage shared on Twitter by the National Police Air Service shows an object which could not be seen with the naked eye, accompanied by the caption, ‘Any suggestion??’ and an alien emoji.

The UFO was filmed by a police helicopter 1000ft above the Bristol Channel

Some have suggested it could be a balloon or a Chinese lantern, but police have ruled out both ideas because of the heat and movement.

The mystery craft was said to be flying against the winds at the time and was said to be undetected by air traffic control.

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Mr Heseltine said his investigation has included several Freedom of Information Requests to South Wales police to obtain flight maps and audio from the cockpit.

He said: “I’ve waited until now to see how much information I could obtain from the police via the FOI requests I’ve submitted. What I can say is that in my opinion the police have not been as open and transparent as they could have been.”

He claims the case bears a resemblance to another case in Chile where a Navy helicopter captured a UFO on infra-red, the Mirror reports.

Gary added: “I believe this British case is a major UFO event and should be the subject of a scientific enquiry.”

It is understood the footage was captured over Bristol on Saturday, September 17 2016, and shared online by NPAS St Athan, the National Police Air Service which is based in South Wales, more than a week later.

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They explained to their Twitter followers that the footage, which says it was 8.30pm, was actually taken about 9.30pm when it was pitch dark.