Around 45 per cent of fitness to practise enquiries received by the GMC last year were about GPs, GMC figures show.
Enquiries about non-GP/specialists were the second most common, but make up just 22 per cent of the total.
However, 45 per cent of cases appearing before fitness to practise panels related to non-GP/specialist doctors.
Just 37 per cent of the cases that came before these panels related to GPs. In total, 27 GPs were erased from the register at a fitness to practise hearing.
GMC data show that in total, 270 fitness to practise hearings took place in 2009, compared with 204 in 2008. The GMC said the increase is linked to a rise in the number of enquiries made from the NHS, police and other public bodies, which has risen significantly since 2006.
'Referrals from these groups are likely to be more serious and therefore more likely to progress through to a public hearing,' the GMC said.
The most common allegation resulting in removal from the register in 2009 related to 'improper relationships with patients', which accounted for 15 cases in total, the GMC said.
Paul Phillip, GMC director of standards and fitness to practise, said the regulator did not know why cases against doctors had increased.
'I'm afraid there are no hypotheses,' he said. 'We are not saying that we haven't thought about it, nor that we haven't chewed the idea over that it has something to do with revalidation, or licensing.
'The reality is that we have absolutely no way in which we can say that's why it is.'