Critics accused the Government of "passing the buck" over contentious decisions to an unelected committee which was answerable to no-one.

But public health experts said an attempt to "depoliticise" decisions about the health of millions could help to restore public confidence in a national programme which has been badly damaged by concerns over the safety of the MMR vaccine.

Under the new law, all decisions taken by the Joint Committee on Vaccination and Immunisation, backed with evidence showing the jabs are cost-effective, must automatically be authorised by the secretary of state for health.

Although until now the health secretary has always followed the committee's recommendations he has retained the right to overrule them.

Pressure group Jabs, a support group for families who believe their children have been damaged by vaccines, said the change was "undemocratic", expressing concern that a body which was "answerable to no-one" would have the final authority.

Campaign founder Jackie Fletcher said: "The committee is a voluntary advisory body made up of medical professionals which includes members with potential conflicts of interest, because of direct and indirect links with vaccine manufacturers."

She expressed fears that the move would allow the Government to go further in extending the national vaccination programme, or making its use compulsory, by using the excuse that it is only following the orders of its advisers.

However, the change was welcomed by Dr Alan Maryon Davis, president of the Faculty of Public Health.

He said: "I think any move to depoliticise this area is welcome."

"The scientists who sit on the committee are eminently competent to come to the right decision, and because these are areas which are highly sensitive, and can become quite political, it seems better to leave the judgements to those who are not liable to get so caught up in the controversies"