Direct Health 2000 says it has 10,000 children on its books waiting for the single mumps vaccine.

Managing director Sarah Dean said 65,000 children had received single jabs in place of MMR at its network of clinics.

There is now a substantial body of research that shows, as far as you can ever show a negative, that there is no link between MMR and bowel problems or autism   Dr David Elliman

Most had completed the course, she said, but there was a backlog for the single mumps jab.

Ms Dean said the company was allowed to import only 25 doses of vaccine per shipment, which was not enough to meet requirements.

The vaccine has been cleared for use by private doctors in the UK but is not available on the NHS.

"If parents choose to go the single route, that's their right to choose," she told BBC News Online.

"It's not for the Department of Health to interfere with their health care choices for their children."

'No need' for single jab

Ms Dean, a 37-year-old mother of five, claims her son, now 16, was damaged by MMR at the age of 8.

The MMR vaccine has been linked to autism and bowel disorders. However, the medical establishment is adamant that such a link does not exist.

Dr David Elliman, Consultant in Community Child Health at St George's Hospital in South London, is among the majority of doctors who back the MMR campaign.

"There is now a substantial body of research - from the US, UK, Sweden and Denmark - that shows, as far as you can ever show a negative, that there is no link between the vaccine and bowel problems or autism," he said.

"Therefore there's no need for the single vaccine."

Dr Elliman said concerns had been raised about the reliability of some types of imported single mumps vaccine.

"Imported mumps vaccines have in the past been unreliable or unsafe," he told BBC News Online.

A spokesperson from the Department of Health said a strain of single mumps vaccine known as Jeryl Lynn was cleared for use by private practitioners in the UK.

Only 25 doses per day can be imported due to regulations imposed by the Medicines Control Agency, he said.

Weight of history

The MMR debate is being discussed on Tuesday at London's Science Museum.

The public will be able to voice any concerns or fears they have to panellists both for and against the triple jab.

Dr Tim Boon, head of collections at the Science Museum, said immunisation has always been controversial because it is one of the very few interventions that medicine asks healthy people to undergo.

"Looking at its history can help us understand the complex factors that come into play when healthy people assess the risks and decide whether to be immunised or whether to have their children immunised."

Huge controversy surrounded the introduction of smallpox vaccination by Edward Jenner in 1796.