Bereaved parents have spoken of their distress at claims links between so-called mad-cow disease and its human form are unlikely.

Ron and Marilyn Carter of Cross Roads, Keighley, have dismissed comments made in the British Medical Journal, that the link is "open to question."

Their son Andrew, an undergraduate at the University of Westminster, died aged 27 of new variant Creutzfeld-Jacob Disease (CJD) in February 2000.

Writing in the British Medical Journal, Dr George Venters disputes the link between bovine spongiform encephalopathy (BSE) and the human form new varient CJD.

The human brain disease has been linked with eating beef infected with BSE.

Dr Venters, an epidemiologist and consultant in public health, said: "Cases have been appearing since 1994. Their rate of increase falls far short of what would be expected were this a food-borne infection.

"There is not clear evidence and the existing criteria used to establish the links between BSE and new variant CJD are far from robust."

He suggests the new variant was no more than the original condition identified in 1913.

But Mrs Carter said: "His remarks are very distressing. He is saying we are liars.

"I don't have any doubt that Andrew died from new variant CJD and he got it from eating meat. All the experts say that without reasonable doubt it came from meat."

Mr Carter, a retired teacher, said he regarded Dr Venters' comments as rubbish.

"I have every confidence in Professor James Ironside of the CJD surveillance unit, who has carried out lots of research and is convinced of the link."

Professor Ironside, who runs the unit at Edinburgh University, said it was "implausible" that both BSE and variant CJD arose at the same time.

Although BSE had not yet led to a rise in cases in its human form, he said the time interval was consistent with the ranges for incubation periods that he expected.

A Department of Health spokesman said the most likely cause of new-variant CJD was exposure to BSE-contaminated food products.