Francis Hall's son Peter died of vCJD in 1996

Francis Hall, from Chester-le-Street, is secretary of the Human BSE Foundation, and says fresh evidence about vCJD means action must be taken.

Her son, Peter, died in 1996 after developing the disease.

A report in the Lancet medical journal suggests that more people are at risk from the condition.

Following analysis of a probable transmission of vCJD via a blood transfusion, scientists found the patient's genetic make-up differed from that of any other person so far diagnosed with the disease.

This suggests that wider groups of people could be at risk than was thought, according to the Lancet.

Ms Hall said she hoped the government would step up research into developing a test for the disease.

Once we have a blood test, it will do away with a lot of the problems, because we'll be able to test people before they have operations Francis Hall, Human BSE Foundation

She said: "There could be many people walking around incubating the disease without showing the symptoms.

"These people could be having operations, donating organs, even just going to the dentist. It's quite frightening.

"Blood tests are being worked on worldwide but unfortunately it appears to be very difficult to pin down.

"Once we have a blood test, it will do away with a lot of the problems, because we'll be able to test people before they have operations.

"Unfortunately, the Government is waiting until the problem is proved before they do something about it."

So far, 142 people have probably or definitely died from vCJD. Most are thought to have acquired the disease by eating infected beef in the 1980s.