There is no link between MMR vaccination and autism or inflammatory bowel disorders based on the evidence that is currently available

Professor Alan McGregor, King's College, London

Professor McGregor told BBC News Online: "There is no link between MMR vaccination and autism or inflammatory bowel disorders based on the evidence that is currently available, although the responsibility of the Department of Health and the MRC is to keep a watching brief on the field."

Professor McGregor said it was important that parents did get their children vaccinated against measles, mumps and rubella.

He said: "I feel very strongly that parents should be encouraged to vaccinate their children.

"The consequence to a much larger population of not vaccinating is enormous - if vaccination rates continue to fall we are in danger of a serious outbreak of these diseases."

Professor McGregor's group did, however, admit that much more research is required into autism and IBDs.

Major study

In a separate development, the MRC has announced a major study into autism.

The study, to be led by Professor Andrew Hall of the London School of Hygiene and Tropical Medicine, will attempt to find out what causes the condition.

Partly because of its rarity, we know very little about what causes autism

Professor Andrew Hall, London School of Hygiene and Tropical Medicine

The researchers will study whether autistic children have a history of other conditions or medical problems, for example, problems during birth.

They will look at whether viral infections in the womb or soon after birth appear to play a role in producing autism.

By looking at a representative sample of health records drawn from over 2 million people registered with 300 general practices across the UK, the researchers will also be able to examine any possible association between autism and the MMR vaccine.

Professor Hall said: "Partly because of its rarity, we know very little about what causes autism.

"Most of the studies to date have been small and have not considered all the possible risk factors simultaneously.

"We hope our study will begin to answer some of the questions about this important developmental disorder."

Measles can kill, but is more likely to lead to serious complications, particularly in the very young. These can include pneumonia or bronchitis, convulsions, and even meningitis.

Mumps, characterised by painful and swollen glands in the head and neck, can cause permanent damage to the testicles, nervous system and hearing.

And Rubella, or German Measles, if developed late in pregnancy, can lead to serious birth defects such as deafness, blindness, cardiac problems and brain damage.

Official figures released last September showed that the number of toddlers receiving the MMR vaccination had risen for the first time in two years.

The controversy surrounding MMR was sparked by a study led by Dr Andy Wakefield of the Royal Free who found that children developed symptoms of autism after the vaccination.

When Dr Wakefield's research was published in The Lancet medical journal two years ago it sparked fears about the safety of the triple jab and led to a decline in the number of toddlers being vaccinated.

An independent panel of experts, who were called together shortly after the initial report caused such a stir, concluded there was no evidence to support a link.