Parents of a 27-year-old man who died of the human form of BSE said their son never ate school dinners and as a baby was fed only home-made food.

Marilyn Carter, whose undergraduate son Andrew, died earlier this year, says: "He took sandwiches to school. All my children did. And when he was a baby I fed him on our own food minced up. I thought that was better for him."

Experts fear that because of a high proportion of young people who have died of new variant Creutzfeld-Jakob disease, it could have been spread through school dinners and mass-produced baby products.

Victims' families are calling for more research following the claims by Dr Robert Will, director of the Government's CJD surveillance unit, that one explanation for the deaths could lie in the amount of mechanically extracted meat in the food of babies and children in the 1980s.

He said baby food and school dinners could have contained remnants of the spinal cord, one of the parts of a cow which becomes most highly infected when animals develop BSE.

Andrew's father Ron, of Cross Roads, says: "Andrew did eat an awful lot of burgers when he was about 16 and 17 and working in Keighley. Andrew was a big lad - he was 6ft 4in tall and 16-stone - so he would often have two lots, especially if there was a promotion.

"I have always thought that the disease came from the cheaper meats and mince that are in burgers."

A Department of Heath spokesman said: "Everybody knows that the use of mechanically recovered meat in the 1980s was a potential source of tissue for new variant CJD, but nobody should be in any doubt that this is not the case now."