Children who have the MMR vaccine are at higher risk of seizures for two weeks afterwards, a study has shown.

Despite the increased risk, there were no long-term adverse consequences and the benefits far outweighed the drawbacks, the research, from the Center for Disease Control in Atlanta, said.

The study is, despite that, certain to be cited by campaigners against MMR, a vaccine for measles, mumps and rubella.

A poll conducted on Wednesday for the Today programme on BBC's Radio 4 found 79 per cent of parents surveyed believed there should be a public inquiry into MMR's safety. Two-thirds said they should have the option of separate vaccinations for their children.

The study, one of the largest ever conducted, examined records of 137,000 children vaccinated against MMR and 340,000 vaccinated against DTP (diphtheria, tetanus and pertussis) in the United States between 1991 and 1993.

It found that between 25 and 34 children per 100,000 who were vaccinated with MMR had seizures between eight and 14 days afterwards. Between six and nine children per 100,000 who had the DTP vaccine were affected, but only on the day of vaccination.

The researchers say in the New England Journal of Medicine that the findings are in line with earlier reports and, in relation to MMR, are consistent with "the onset of fever after vaccination with live attenuated measles virus". The children who suffered seizures were no more at risk of long term neurological or developmental problems than other children who had seizures not linked to vaccination, they said.

The editors of the Journal said: "The benefit of the vaccines far outweighs the morbidity from seizures."

Responding to Today, the Liberal Democrat health spokesman Evan Harris said that science should not be a slave to opinion polls. "Medical research must proceed on the basis of published, properly scrutinised data. All the data so far suggests that the MMR vaccine is the safest option."