Campaigners were calling for more research to be conducted following new evidence from the the United States suggesting a link between measles, mumps and rubella vaccine (MMR) and autism.

Scientists at Utah State University in Logan have found a strong association between the vaccine and an autoimmune reaction thought to play a role in autism.

David Potter, head of information and policy at the National Autistic Society, said: “The NAS would be keen to see further independent research to replicate these findings, which might provide a way forward in understanding and treating the condition.”

Keith Lovett, of Autism Independent UK, said: “Parents have been suspecting this for many years now but research was needed in the area to back it up or put it to bed.

“It’s certainly not going to go away until it’s done properly. Proper trials are needed. Supposed research has been done by the Government but there are different weights of research as you know.

“This research has to be replicated by other researchers to get the full weight behind it. We have to sit and wait a little while longer so people can back it all up with more evidence.”

The team led by Dr Vijendra Singh analysed blood samples from 125 autistic children and 92 children who did not have the developmental disorder.

The researchers found a “significant increase” in the level of MMR antibodies in the autistic children.

Part of the measles component of the vaccine caused an unusual anti-measles response in 75 of the autistic children, but not in the normal children.

More than 90% of the autistic samples which showed an immune response to MMR were also positive for antibodies thought to be involved in autism.

These antibodies attack the brain by targeting the basic building blocks of myelin, the insulating sheath that covers nerve fibres.

Dr Singh has suggested that this autoimmune response may be the root cause of autism.

The US scientists, who report their findings in the latest issue of the Journal of Biomedical Science, concluded: “Stemming from this evidence, we suggest that an inappropriate antibody response to MMR, specifically the measles component thereof, might be related to pathogenesis of autism.”

Dr Singh has published previous work indicating a link between MMR and autism. He has argued for years that autism can be traced to an autoimmune reaction centred on the brain.

David Potter of the National Autistic Society said: “This current research offers a plausible explanation of underlying pathophysiology in some children with autism.

“Although the National Autistic Society has yet to see the full paper it welcomes such studies into the underlying pathophysiology in these children.”

The new study will fuel more controversy over MMR fears, which have been blamed for downturns in the number of children being vaccinated.

MMR vaccine uptake in the UK for 16 month-old children dropped from 76.2% to 70.1% between December and March, but then rose to 72% in April.

Immunisation for 24-month-old children fell from 85.8% to 84.4% over the same winter period and then increased to 85.9%.

The Public Health Laboratory Service said the dips were probably due to “intense adverse publicity” about MMR over the Christmas and New Year period.

The PHLS, Department of Health and British Medical Association have all consistently driven home the message that the vaccine is safe.

Public health experts have warned that low uptake of MMR could increase the risk of measles outbreaks.

But the pressure group Jabs (justice, awareness and basic support), which believes parents are right to be worried about MMR, said the new research strengthened its case.

Jonathan Harris, the group’s West Midlands spokesman, said: “The evidence is building up tremendously. I really feel there’s a very, very strong case now for suspending MMR use while further investigations are carried out.

“We have said all along that it affects only a certain subset of children, causing a new type of autism in children whose immune systems have not really been tested fully.”

He stressed that Jabs was not anti-MMR but wanted parents to be allowed to choose single rather than multiple vaccines.

“At the moment parents only have the choice of MMR or nothing,” he said. “We think that’s irresponsible of the Department of Health.”

Keith Lovett, of Autism Independent UK, said the Government had “bullied” parents into using the MMR vaccine, making it harder for them to get access to single vaccine.

“Certainly the Government has gone out of its way to make sure you can’t get singles. You have to have inoculation of the triple or nothing at all.

“There are lots of questions which now come into play, like: ‘What are they (the Government) hiding behind?, is the Government in hot water if there is an association?, will there be claims against the Government?.”

Both the BMA and the Department of Health said yesterday they could not comment before allowing experts to look at the full research paper.