The man who discovered BSE, Nobel Prize-winning American scientist Professor Stan Prusiner, said yesterday that every Briton should be tested for variant CJD, which has killed 117 people in the UK since 1995.

Today, the director of the CJD Surveillance Unit, Professor James Ironside, said large-scale testing for the illness would be "helpful". He said: "Because of the uncertainty, any steps we can take to try to define what the future problems might be would obviously be very helpful and that is one of the reasons why he has advocated more emphasis on diagnosis and screening.

"The problem could be very large indeed. We simply don't know. I think that some form of screening approach to define the magnitude of the problem would therefore be helpful," Professor Ironside told the BBC Radio 4 Today programme.

Professor Prusiner, of the University of California, San Francisco, is in Britain to discuss research into the disease.

He said yesterday: "A million cattle infected with BSE entered the British food chain so almost everyone in the country will have been exposed to the infectious prion proteins that cause variant CJD.

"Every Briton should be tested so that if they are developing the disease it can be spotted before symptoms appear."

But Frances Hall, secretary of the Human BSE Foundation, whose son died of vCJD in 1996, said screening would wreck victims' lives without offering any hope of treatment.

"There is not any treatment or cure for this disease," she told the Today programme.

"Would people want to be told they are incubating a dreadful disease and be told that nothing can be done?

"It really won't serve any useful purpose at all, other than to end their lives there and then."

Positive tests would make it impossible for victims - many of them at the start of their adult lives - to get access to financial services like mortgages and life insurance, she said.

No test currently exists for vCJD in living humans, and Professor Ironside said greater efforts should be devoted to developing one.

"In vCJD, the prion is present outside the brain probably for a long time in the incubation period and that is the window of opportunity to develop a diagnostic case, preferably based on blood, so we can try to define the scale of the problem," he said.

"We haven't done that and I think much more emphasis needs to be placed on that and I think the national emphasis needs to be based on early diagnosis of this group of diseases."

New figures released today show that to date in the UK 119 people have died from definite or probable cases of variant CJD.

The statistics, published today by the Department of Health, show there were 93 deaths which were confirmed cases of vCJD.

The remaining 26 are classed as probable vCJD, because there has not been pathological confirmation from post mortem examinations, or because the confirmation is still pending.

It is thought there are around 10 vCJD cases still alive.

Overall the total number of definite and probable vCJD cases, dead or alive, is 129.