Has Jaws found a new home in our waters?

Evidence is mounting that great white sharks, the world's most fearsome marine predators, sometimes appear off the coast of Britain, according to a new television documentary.

A BBC team re-examined records from fishermen and holidaymakers closely and came to the conclusion that "Jaws" could be straying into British waters.

Many of the numerous alleged sightings are believed to be basking sharks, the huge fish - the world's second largest - which are fairly numerous off our west coast in summer. Though they have a menacing dorsal fin like the great whites, they feed entirely off plankton and leave humans alone.

But some accounts look more convincing. In particular, a 2003 sighting by a group of divers off the west coast of Scotland appears plausible to the makers of Great Whites - Great Britain?, to be shown on BBC 1 tomorrow night.

One of the divers was a marine biologist, Simon Greenstreet. "The shark approached and swam alongside the boat, very much giving us the once over ... this was absolutely definitely not a basking shark," he tells the programme.

"I was convinced in my own mind that this was a great white shark - I could think of nothing else that this could be."

The programme's producer, Anuschka de Rohan, says the account of this sighting changed her views. "A lot of the sightings are just people who have seen basking sharks and thought it must be Jaws, and they can be ruled out," she said.

"But this sighting made me change my mind, and as we made the programme I have come round to the conclusion that they could well be here."

Some marine biologists still reject the possibility of Carcharodon carcharias coming as far north as Britain - the nearest undisputed sighting is the Bay of Biscay. On 24 May 1977 three French fishermen caught a juvenile great white, nearly seven feet long and weighing more than 200kg, in nets set 15 metres deep off the French port of La Rochelle.

But Ms de Rohan thinks the possibility of a British visit is real. "Great whites can travel huge distances," she said. "One was tagged travelling from South Africa to Australia and back - a round trip of 19,000km (11,800 miles). There are populations near the Azores and in the Mediterranean, so a journey up here isn't out of the question. And our water temperature is suitable, even though some people think it is too cold."

Another sighting examined by the programme was in the summer of 2002 by a lobster fisherman, Brian Bate. He got the shock of his life when, as he was heading towards his regular fishing ground off Padstow, Cornwall, he saw something huge leap out of the water. "I thought, what was that! It was quite a size to come right out of the water ... when I approached there was all this blood in the water, which sort of alarmed me," he says. Had Mr Bate just witnessed a great white shark attack? And, if so, what was it attacking?

The programme suggests it could have been the great white's favourite prey, seals, as Britain has one of the biggest populations of seals in Europe. And it examines a photo of a badly injured seal that was washed up on the Welsh coast. A well-known shark expert, Ian Fergusson, giving his opinion on the injuries, said: "Had this washed up in South Africa, I guarantee you my colleagues and I would have looked at it and thought, 'oh yes, it definitely looks like an attack by a white shark'."

* Great Whites - Great Britain?, presented by Steve Leonard, is on BBC1 tomorrow night at 7pm.