The government's chief medical officer has sought to reassure people worried that they could contract CJD - the human form of BSE - through routine operations.

Professor Liam Donaldson told the BBC's Today programme that measures were already in place to protect people.

And he said experts would review the measures in the light of the findings of a King's College report into tests for CJD.

However, he cautioned that the study only looked at a small sample of people.

Disposable instruments

The report found that evidence of CJD can be found in the tonsils of people suspected of carrying the disease.

It also suggested there could be a danger of the disease being passed through routine operations.

Professor John Collinge, who led the research, called for the use of disposable instruments to prevent the spread of disease.

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But Professor Donaldson said this might not be practical because modern surgery often required highly engineered surgical appliances.

Replacing them would not be easy and any decision had to be balanced against the health risks of using more easily disposable instruments.

He said that since last April doctors instruments used on suspected CJD patients were routinely destroyed.

He added that government experts had also begun research into a general population survey of the CJD risk to the wider population, based on a study last year showing traces of the disease in the appendix of a person who died from CJD.

This suggested that appendices could offer advance warning of the extent of CJD in the general population.

Previously, diagnosis of nvCJD has had to wait for a brain biopsy on death.

Frightening

Conservative health spokesman Alan Duncan said he had been warning of concerns about routine operations for at least six months and had sent letters to Health Secretary Frank Dobson on the subject.

Mr Dobson is also said to be concerned about the risk of spreading the disease.

Roger Tompkins, whose daughter died from nvCJD last year, said: "It is quite frightening that the disease could be spread through ordinary operations on the instruments used.

"Anything which can stop this disease from spreading is a major priority."

Medical experts told him his daughter had died from eating infected beef before 1985, when she became a vegetarian.

He added that she could also have become infected from other products, such as medicines, which contain beef products although this is not listed on the ingredients on the packet.