Tony Blair today is accused by the Tories of a "cynical" move by leaking the fact that his son, Leo, has had the MMR vaccine. Downing Street refused to comment on the disclosure in The Independent this weekend that Leo had the controversial MMR jab last week.

It came as fears of a measles outbreak grew with confirmation that three children had contracted the illness and 22 cases had undergone tests in south London where vaccination rates have fallen dangerously low, to 70 per cent.

Dr Liam Fox, the Tory spokesman on health, said the Blairs should make a full disclosure of Leo's MMR jab to persuade other doubting parents to follow their lead. "If the reports are true, it is an astonishingly cynical move designed to deflect criticism from the Government's abject failure of policy on MMR which has put innocent children at risk," he said.

The immunisation controversy will be fuelled tonight by a BBC Panorama programme "MMR – Every Parent's Choice".

London's regional director of public health, Sue Atkinson, said the south London outbreak was the result of parents rejecting MMR for their children. She said she had "no doubts" that MMR was safe.