Health chiefs today urged parents not to turn their backs on the mumps, measles, and rubella - MMR - vaccine after a report linked it to chronic diseases, including autism, in children.

A new study of children who developed the brain condition after an apparently healthy infancy found that 24 out of 25 of them had the measles virus in their gut.

Researchers said the virus could have come from the combined mumps, measles and rubella vaccine, which is given to hundreds of thousands of children in Britain every year.

Professor John O'Leary, of the Coombe Women's Hospital in Dublin, and Dr Andrew Wakefield, of London's Royal Free Hospital, presented their research to the United States Congress last Thursday and said there was "compelling evidence" linking autism with MMR.

But the Department of Health rejected the study and said parents should continue to trust the MMR jab.

"This is a highly selective sample carried out with incorrect and inappropriate controls and unverifiable by usual scientific means," said a Department of Health spokeswoman.

"As such it is uninterpretable. It does not prove anything and there remains no evidence to suggest there is any link between the MMR jab and autism.

"It would be a disaster if children were to die of vaccine-preventable diseases over unfounded vaccine safety scares."

The research is the latest scare over the MMR vaccine, which has previously been linked to a number of health problems, although other studies have given it the all-clear.