The number of complaints about doctors made by their colleagues or patients is on the rise, according to new figures.
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 8,109 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 5,014.
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 is 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 are more likely to complain than men.
GPs were more likely to be complained about than other doctors and male doctors overall were twice as likely as female doctors to attract complaints.
Some 22% of male GPs received a complaint compared with 11% of female GPs between 2007 and 2012.
The proportion of doctors aged over 50 who received a complaint was higher than for doctors aged 30 to 50. This was particularly true for GPs, the State of Medical Education and Practice report showed.
A third of all complaints received met the threshold for a full investigation by the GMC. Only 20% of complaints from the public met the criteria for investigation, compared with 84% from employers and 48% from individual doctors.
Professor Sir Peter Rubin, chair of the GMC, said: "Overall the standard of care that patients receive in the UK is good and doctors continue to deserve the trust and respect of the public.
"The GMC has an important role to play in protecting patients and ensuring that doctors practise to the highest possible standard.
"Complaints from members of the public, doctors and other professionals are invaluable in helping us to do this.
"Complaints also give the health service a chance to reflect and improve the care that patients receive.
"However what our report shows is that some patients don't know where to go to raise a concern about their treatment and more needs to be done to help them raise issues.
"Making a complaint about a doctor can be stressful and it is important that concerns are raised with the right organisation so patients are not passed from pillar to post."
Dean Royles, chief executive of the NHS Employers organisation, said: "The GMC's findings should help reassure the public that concerns about care are being identified earlier, reported more often, and resolved more swiftly.
"There is every sign that doctors are increasingly confident to highlight concerns about the practice and behaviour of colleagues and that these will be addressed without fear of recrimination.
"This is the culture of transparency that we are striving for in all parts of the NHS, and we won't allow our focus on it to slip."
Anna Bradley, chair of Healthwatch England, said: "It's no surprise that people don't know who to go to with their complaint as the system is far too complex.
"Most patients and people receiving care don't know the difference between the GMC, the Care Quality Commission and their local complaints advocacy services. They just want their complaint dealt with.
"But people aren't just failing to report complaints because they don't know where to go.
"We know from our own research that more than half of those who experienced a problem in the last three years didn't report it because they simply didn't trust the system to listen or take any action.
"We all have a right to safe, dignified and high quality care, backed up by an effective complaints system for when things go wrong. The Healthwatch network can play a central role helping people understand where to go with their complaint, making things as simple and straightforward as possible."