Data from the General Medical Council (GMC) shows a jump in both patient complaints and the number of doctors willing to speak up about the poor standards of other medics.
In 2012, the GMC received 8109 complaints - a 24% increase since 2011 and a 104% increase since 2007.
Most complaints about doctors come from patients and from relatives and friends of those patients. Between 2007 and 2012, the overall number of complaints from the public rose by 87% to 5014.
The rest of the complaints came from a doctor's employer or were made by individual doctors about another doctor's fitness to practise.
The GMC, which regulates around 250,000 doctors in the UK, said the overall number of complaints was very small when the number of interactions between doctors and patients is taken into account.
And it said higher patient expectations and the greater willingness of other doctors to raise concerns could account for the rise.
Overall, 54% of the complaints were about clinical care or both clinical care and communication with patients.
Many complaints from individual doctors (38%) were about issues such as a conflict of interest or criminal convictions held by their colleagues.
Among the public, people aged 46 to 60 were the most likely to complain and women were more likely to complain than men.