Great white sharks are hunting off the Westcountry coast because it provides "perfect" conditions for the predators, leading experts said yesterday.

Some claim the gigantic killers – made famous in Steven Spielberg's 1975 blockbuster Jaws – have been pushed into British waters by a shortage of prey in their usual hunting grounds.

An increase in water users has led to more reported sightings across the UK, including seven credible accounts over the past 70 years – three in the Westcountry.

Experts and conservationists agree that great whites sharks are likely to be found in our waters, but say the famous maneaters have been frequenting the region's coastline for thousands of years.

Steve Mills, an angling expert, claims our coastline is "awash with killer sharks."

He said: "There are definitely great whites in our waters.

"The only reason they do not get caught by fishermen is because they do not use the right tackle.

"They will be here because of the stocks of mackerel and will probably be feeding on pollack and cod. There have been sightings in the past but no photographic evidence, but that does not mean they are not here."

But Richard Peirce, chairman of the Shark Trust, said great whites were more likely to be "occasional, vagrant visitors" to our waters.

Mr Peirce, a shark conservationist and researcher from Bude, has narrowed down thousands of reported sightings of great whites to seven credible accounts.

His research, carried out independently of the Shark Trust, identified "clusters" of reports off the north coast of the Westcountry peninsula, which support the idea of an occasional great white visitor.

Mr Peirce said: "There is no reason why we would not have them in our water – the big puzzle is why we haven't had a conclusive sighting yet.

"The conditions off the West of England are perfect, but not one has been positively identified. Sadly, we've killed off 70 per cent of the white shark population in the Atlantic, so the chances of spotting one are actually decreasing.

"They have probably been in our waters for thousands of years – so this is nothing new – and nobody has been eaten yet."

Mr Peirce's credible sightings include a lobster fisherman off Trevose Head who spotted a large shark jump out of the water with something in its mouth in 2002. When he approached the site, he found a large quantity of blood and seal debris in the water.

There were a series of credible sightings in August 1999 in the seas around Crackington Haven and Bude, and in Looe, Cornwall in July 1970 a group of fishermen describe a suspected great white "spy hopping" – poking its head from the water – as they pulled in their catch. Some of the accounts dismissed by the shark expert as "barking" include a woman who claimed she had seen a great white swimming up the River Ex in Devon, and a man who insisted he had seen one of the predators feeding on seagulls in Lowestoft, Suffolk.

In the summer of 2007 a media frenzy broke out after footage shot by a tourist of a shark breaching off Porthmeor Beach in St. Ives was passed to a national newspaper.

Due to the quality of the footage and stills, experts were unable to say whether or not it was a great white.

Although unwilling to rule it out, Mr Peirce said it was more likely to be a porbeagle, basking or mako shark.