The GMC has seen a huge rise this year in the number of doctors being reported to it with concerns over their fitness to practise.
The monthly rise in cases this year is up 30 per cent on 2008.
The rise may signal that trusts are clamping down on bad doctors in advance of revalidation.
'The referrals are coming mainly from the NHS and they are not trivial,' said GMC chairman Professor Peter Rubin.
'It is likely to be a precursor to the introduction of revalidation. Employers are beginning to take stock,' he said.
The increase is so great that doctors up before the GMC are waiting longer for investigations and hearings.
The GMC admits that it has missed its own targets of nine months for hearings to be concluded and six months for investigations to be completed.
In July, almost a third of cases missed the GMC's self-imposed target of nine months from referral to adjudication hearing.
In 11 cases, doctors waited longer than nine months for their adjudication hearing to start.
In the same month, 50 out of 391 doctors saw their investigation drag on beyond six months.
The council said it expected to be back on track by the end of the year.
GPC negotiator Dr Beth McCarron-Nash said she did not believe the number of doctors needing to be referred to the GMC had actually risen, and urged PCTs to work towards resolving concerns locally where possible.
She added: 'Referral to the GMC is not the way for PCTs to deal with doctors whom they feel are not performing to their best.
'They should look to empower practices and GPs having difficulties to get better, and work with LMCs.'