It would mean that we would only be able to test half the number of patients

Professor Mike Patten, St George's Hospital

It wants the NHS to pay them money - up to �2,000 - every time it tests a woman for the gene.

So far 2,000 UK women have been tested, but the government has not paid the company anything.

Negotiations are underway to resolve the issue, but many doctors are fearful that the price may prove prohibitive and women who need tests may not get them.

If the NHS carries out the tests, the cost is far less, they say.

Professor Mike Patten, head of medical genetics at St George's Hospital, London, told the BBC: "It would mean that we would only be able to test half the number of patients.

There are very large numbers of patent claims for almost any gene of any use

Professor Martin Bobrow

"We would also lose laboratory staff who are highly trained and have spent many years developing specialised skills in the health service."

The BBC understands that the Department of Health is seriously considering offering Myriad the deal that it wants.

Professor Patten said: "We're one of the centres that does as many if not more tests for breast cancer than any other centre.

"We don't seem to be getting consulted in this process."

Other scientists are warning that the benefits of the unravelling of the human genome could be lost to the NHS by widespread gene patenting.

Professor Martin Bobrow, another leading geneticist, said : "As soon as anyone starts developing tests for some other disease, some other person or company may come out the woodwork claiming they own that one.

"There are very large numbers of patent claims for almost any gene of any use."