Dr Mansfield (left) gives a child the single vaccine.
Doctor Peter Mansfield, 58, believes families should have the right to choose single vaccinations instead of the controversial MMR jab as recommended by the Department of Health.
But the health authority in Worcester, where Dr Mansfield runs a clinic, has accused him of putting children at risk, and reported him to the General Medical Council.
The GMC can not only impose a temporary ban on him working, but, if they find him guilty of serious professional misconduct, could even strike him off the medical register.
Parents attending his clinics reportedly pay £42 to register and receive an information pack.
The cost of the vaccines is £35 for rubella, £50 for measles and £45 for mumps.
Up to 400 children have received the single immunisations from Dr Mansfield in Worcester in the past year and up to a further 300 at his practice in Louth, Lincolnshire.
Freedom
Dr Mansfield told Radio 4's Today programme that what he was doing was legal and within normal ethical and professional medical constraints.
"Governments do not dictate to doctors completely," he said.
"Doctors do have some clinical freedom and I am simply exercising the freedom which I have always been granted in the past.
"So far as the safety of the vaccine is concerned I am not entering into that issue, I am simply noting that people want to have measles protection but they do not want it via MMR.
Immunity fears
"What I am doing is making sure they get some protection."
But the director of public health for the West Midlands, Professor Rod Griffiths, said what Dr Mansfield was doing was not appropriate.
"We're all in favour of choice but if people are being offered a choice between something that is safe and that is unsafe then I don't think that's appropriate.
"People naturally assume doctors are reliable. What this reference to the GMC does is it allows a way of deciding whether what Dr Mansfield is doing is reliable or not."
Some have even set up a network of "parties" where families can meet those infected with the illnesses.
They believe that by exposing the youngsters to the diseases they will build up their own resistance to the bugs.
But the British Medical Association's annual conference in July overwhelmingly rejected a motion calling for single vaccines to be made available.
It warned that parents who did not get their children vaccinated were threatening the health of other children.
Uptake of the MMR jab has fallen since concerns were first raised in 1998 that it was linked to a rise in certain disorders.
Immunisation rates have fallen to below recommended World Health Organisation levels, promoting fears that the immunity of the whole population could be threatened.