Campaigners claim the plant is a major polluter

Prof Mackay said the cash would be better spent on preventing the thousands of deaths on the roads or in the home.

"It's a very safe place indeed with a better safety record than almost any industrial site in Scotland.

"There is less radiation present in the environment at Dounreay than the level of radiation coming from radon gas around my house in Aberdeenshire."

The professor accused anti-Dounreay lobbyists of being too "obsessive".

In an interview with The Herald newspaper, he said: "Some people have developed fixations about Dounreay. It is their life.

Nuclear experts

"They are clever and very well informed and they can be admired for that but they are obsessed."

Mr Mackay revealed that he too had been "suspicious" of Dounreay.

But said that people at the site were willing to "communicate openly" about any problems.

The professor, a former director of the Scottish Environment Protection Agency's (Sepa) north region, added: "Sepa now exercises enormous control through four full-time nuclear experts monitoring Dounreay.

I now see that a single campaign has been allowed to damage this installation and through that the whole industry.

Prof David Mackay

"These resources would, in my view, have been better employed monitoring the enormous expansions of salmon farming."

Mr Mackay admitted that he had once said that he would treat Dounreay "as guilty until it proved its innocence".

He said: "My opinion has changed greatly over the years. I now see that a single campaign has been allowed to damage this installation and through that the whole industry."

Kevin Dunion, chief executive of Friends of the Earth Scotland said: "We believe in the principle that the polluter pays.

Nuclear particles

"There is no doubt that Dounreay has resulted in thousands of nuclear particles being left on the seabed in the north of Scotland and these are now starting to appear on the beaches."

An estimated 17 radioactive particles have been found on Sandside Beach in Caithness since monitoring started in 1983.

The particles, which are the size of a grain of sand, are believed to have come from the plant, although the exact source has never been identified.

Mr Dunion said that the plant had polluted the area throughout 30 years of its operation and it should now pay for that damage to be cleaned up.