The doctor at the centre of research linking autism with the MMR jab has rejected claims the work was "flawed".
Dr Andrew Wakefield has denied there was a conflict of interest
Dr Andrew Wakefield mounted his defence in the Sunday Telegraph after the Lancet medical journal said it should not have published the study in 1998.
He said he had "raised important questions about child health".
The General Medical Council confirmed it is to investigate claims by the Lancet that Mr Wakefield had a conflict of interest over the research.
The MMR study prompted many parents to reject the three-in-one jab, even though most experts say it is safe.
Last week Dr Richard Horton, editor of the Lancet, told the BBC he had discovered that the researchers had a "fatal conflict of interest".
Mr Wakefield maintains he acted entirely ethically.
On Saturday Mr Reid urged the General Medical Council to investigate "as a matter of urgency".
A spokeswoman for the GMC said on Sunday: "We are concerned by the allegations
and will be looking to see what action - if any - maybe necessary."
She confirmed they would be speaking to Mr Wakefield in the near future.
The Lancet launched an investigation into the way the study was carried out after it received an "allegation of research misconduct" from the Sunday Times.
The allegations do not cover the actual findings of the study.
Dr Wakefield had been commissioned by the Legal Aid Board to do a separate study to the one reported in the Lancet, said Dr Horton.
Some children were involved in both trials, he said.
Dr Horton said the goal of the Legal Aid Board-funded study was to find out if there was evidence to support a multi-party litigation case by parents who claimed the MMR jab had harmed their children.
"We did not know that he had a dual role with the Legal Aid Board...and we certainly had no idea that he had received money to do that."
Dr Horton said it was "perverse" that Dr Wakefield had accepted the facts of his dual role and that he had received money from the Legal Aid Board, but denied a conflict of interest.
But Dr Wakefield told the Sunday Telegraph: "That was a completely separate study. We took children according to clinical need. There was no selective recruitment."
He added that he was standing by the findings.
"We have identified important illness in children and raised important questions about child health," he added.
London's Royal Free Hospital - where the research was carried out - backed Dr Wakefield in a statement on Saturday, said the Sunday Telegraph.
The medical school told the paper: "We are entirely satisfied that the investigations performed on the children reported in the Lancet had been subjected to appropriate and rigorous ethical scrutiny."
But earlier Dr Horton said the work was against the Lancet's rules in 1998 about declaring conflicts of interest.
"If we had known the conflict of interest Dr Wakefield had in this work I think that would have strongly affected the peer reviewers about the credibility of this work and, in my judgement, it would have been rejected," he said.
He told Today he believed the MMR jab was "absolutely safe".
Last week Dr Wakefield said his findings had been confirmed independently by "reputable physicians and pathologists."