Rising demand by anxious parents for the single jabs for measles, mumps and rubella is causing a shortage of the vaccines, according to one of the main suppliers for family doctors in the South-east.
Andrew McCoig, a community pharmacist in Croydon, said that he ran out of the measles single vaccine before Christmas. Fresh supplies are not due until mid-January.
Mr McCoig also said he was being contacted directly by parents who are using internet web sites to track down single-vaccine supplies as well as doctors who are prepared to administer them for around £50 a jab.
Tony Blair is riding out the storm over his refusal to confirm whether or not his 19-month-old son, Leo, has been given the combined mumps, measles and rubella vaccine (MMR), on the grounds that it would breach his family's privacy.
Officials said that the Government would not reverse its policy and return to providing single vaccines on the NHS. The Public Health Laboratory Service backed Mr Blair, saying it was "inappropriate" for the Prime Minister and other politicians to be pursued by the press over their children's jabs.
Dr Angus Nicoll, the director of the service, said it would be a "long slog" to raise immunisation levels, and he warned that it may be necessary to launch a "catch up" immunisation campaign if the risk of an epidemic becomes clearer. "We are not at that stage yet," he said.
Dr Liam Fox, the Tory spokesman on health, said Britain is facing a "public health disaster" and accused Mr Blair of failing to use the opportunity to show leadership on the issue.
However, Dr Fox refused to endorse the campaign by his Tory backbench colleague, Julie Kirkbride, for parents to be given a choice of single jabs for their children.
"MMR is the safest. All the evidence suggests that it is the safest thing to do. But the Government has a duty of leadership to make sure that immunisation rates are kept up," he said.
"We are heading for a public health disaster if we don't get immunisation rates up. The Government has contributed to this by sheer negligence," he added.