The American researchers were told to leave the RCN's head offices in central London when they arrived to set up their press conference early this morning.

A spokesman for the researchers said RCN officials gave them only a few minutes to pack up and find another venue.

The research, published today in the medical journal International Pediatrics, found a significant link between the mumps, measles and rubella jab and autism compared with another triple jab given to children.

But an RCN spokeswoman said the college could not be seen to be endorsing the findings in any way.

She said: "People would have implied that the RCN considered the MMR vaccine to be unsafe, which isn't the case. We are very supportive of MMR.

"Therefore it did not seem appropriate for us to host this press conference."

The spokeswoman said college officials only knew the content of the report late last night, although the researchers dispute this.

The authors, Dr Mark Geier and David Geier, drew their findings from a database set up by the US centres for disease controls and protection to enable health workers to report adverse reactions to childhood vaccines.

The study looked at reports of suspected neurological problems after the MMR jab and the diphtheria, tetanus and pertussis (DTP) combined vaccine.

Between 1994 and 2000 almost 25m first doses of MMR and around 63m doses of DTP were given to children.

Among those given MMR, there were 133 reports of suspected neurological problems such as autism, mental retardation or brain damage.

There were 29 reports of autism among boys, eight among girls and the relative risk was five times higher in those given MMR compared to DTP.

The authors concluded that MMR was associated with a marked increase in neurological disorders compared to the DTP vaccine.

They said the MMR programme should carry on but using dead instead of live forms of the viruses.

UK groups campaigning for single vaccines said the study justified their concerns about the jab and called for a public inquiry into its use.

Jonathan Harris, of the campaigning group Jabs, said the study "completely vindicates the concerns of both the parents and carers of the children affected".

"We now call upon the government to hold a public inquiry and conduct a total review of their childhood vaccination programme and to suspend the use of MMR whilst further independent studies are made and make single vaccinations available on the NHS."

But the health protection agency (HPA) and the Department of Health (DoH) said the study was seriously flawed.

Dr Mary Ramsay, consultant epidemiologist at the HPA, said: "This research is seriously flawed - it compares children of different ages who have received different vaccines and the conclusions are incorrect."

She said MMR was given at 15 to 18 months of age whereas DTP vaccinations were given at two, four and six months.

"Regardless of the other weaknesses of the data, the failure to compare children of the same age is enough to explain the apparent excess of cases reported in the MMR group," she said.

Dr Ramsay said the findings contrasted dramatically with other studies that have used valid methods and found no increased risk of autism following the MMR jab.

The link between MMR, autism and bowel disorders was first raised by Dr Andrew Wakefield in 1998.

Dr Wakefield, who is now the chief medical scientist for Visceral, a charity which funds research into bowel problems and autism, said: "Based on this study and others, it is now untenable for the DoH to refuse parents a right to choose the individual vaccines in preference to the MMR for their children."