A fitness-to-practise panel said its findings, including dishonesty and misleading conduct, 'would not be insufficient to support a finding of serious professional misconduct'.
The finding by the GMC after two-and-a-half years of investigations is a further nail in the coffin of the anti-MMR lobby.
The panel will meet again in April to decide if Dr Wakefield is actually guilty and whether or not to impose restrictions on his practice, such as being struck off.
Dr Wakefield's research findings, published in The Lancet in 1998, led to a drop in MMR vaccination rates and a rise in measles cases as well as arguments between GPs and the parents of babies due for their MMR jabs.
The GMC found that Dr Wakefield acted unethically and that his behaviour in respect of the Lancet paper was 'dishonest and irresponsible'.