A child health expert who worked on the first research which linked the measles, mumps and rubella (MMR) vaccine with autism said yesterday that he now believes the injection is safe.

Simon Murch, a consultant paediatrician at the Royal Free Hospital in London, also rounded on his former colleague, Dr Andrew Wakefield, accusing him of being "completely wrong" and obsessed with trying to prove that MMR may cause autism.

Mr Murch worked with Dr Wakefield on the 1998 research paper which first raised concerns that the measles, mumps and rubella vaccine could trigger autism in children. The study, published in the medical journal The Lancet, caused MMR uptake to plunge, and has been mired in controversy.

Dr Wakefield says he was forced out of the Royal Free because his findings were so explosive. He now works in the US, and has published further research suggesting there could be a link. He has also questioned the way in which the vaccine was tested before being launched in Britain.

Mr Murch said he had decided to speak out because he feared Britain was on the brink of a major measles epidemic after the scare had caused uptake to fall to critically-low levels. In a letter to The Lancet, Mr Murch says: "There is now unequivocal evidence that MMR is not a risk factor for autism - this statement is not spin or medical conspiracy, but reflects an unprecedented volume of medical study on a worldwide basis.

"By any rational standards of risk-benefit calculation, it is an illogical and potentially dangerous mistake for parents to be prepared to take their children in a car on the motorway or in an aeroplane on holiday, but not to protect them with the MMR vaccine."

Mr Murch told The Independent: "When we did the first research in 1998 we did not say that MMR triggered autism. We discovered a link between a certain type of bowel lesion and autism and that has since been replicated in other research. The link between MMR and autism has not. In 1998 we asked a question about whether there could be a link. I think that was a reasonable question to ask. I believe that question has now been answered - there is not."

He said: "Andrew Wakefield is a personal friend and I think he is well intentioned, but I think he has got this completely wrong ... His focus is not that of a paediatrician any more. He is coming from a single position of thinking there is a link between MMR and autism, a position which is not supported by any data. He has been forced onto the back foot by the hostile reception he got from the first paper, and it has become very difficult for him to say 'I think I was wrong.'"

Mr Murch said Dr Wakefield and other researchers were being irresponsible in making continued claims about a link without publishing research to support their declarations.

"We keep getting these claims and leaks to the press and drips of research, but there has been no proper large-scale study with controls, published in a respected, peer-reviewed journal," he said.

"We really have reached the critical point with uptake of MMR, and I do believe that we are on the brink of a very nasty epidemic."

The World Health Organisation states that 95 per cent of children need to be vaccinated in order to ensure "herd immunity" protection for the whole community.

Uptake of MMR has fallen to as low as 61 per cent in some parts of London, and there are now increasingly frequent outbreaks of mumps and measles in the capital. Doctors have repeatedly warned that diseases such as measles and mumps can be fatal or cause severe handicap and are of greater risk to children than the MMR vaccine.

A spokesman for the Department of Health said: "Parents can be reassured by Mr Murch's comments ... His letter is a clear reminder of the importance of immunisation with MMR."