Nick Hardwick has come in for fierce criticism from rank and file police
Rank and file police have criticised the Independent Police Complaints Commission, accusing its leadership of conducting a witchhunt.
The Police Federation said IPCC chairman Nick Hardwick, who is leading an inquiry into the G20 protests, was acting like a "witchfinder general".
Members are angry that Mr Hardwick gave media interviews in which he expressed criticism of officers' behaviour.
So far the IPCC has received 185 complaints following the G20 protests.
More than 80 are from people who say they were assaulted or witnessed an assault by police, more than 50 are about police tactics and more than 40 were general complaints from TV viewers.
Federation chairman Peter Smyth said he had written to the government to complain about Mr Hardwick.
He said: "Keen, apparently, to don the mantle of witchfinder general, Mr Hardwick discusses some selective aspects of G20 and passes lofty and withering judgment on London's police officers.
"His job is - or should be - to consider the evidence for or against misconduct dispassionately and then present his findings to the proper authorities, such as the Crown Prosecution Service or the coroner."
In a newspaper interview at the weekend, Mr Hardwick said he had "serious concerns" about frontline supervision of officers at this month's demonstrations.
He also said police needed to remember they were "servants, not masters" of the people.
But Mr Smyth said giving the interview was "totally irresponsible" because the IPCC was conducting a criminal investigation into officers' conduct.
An IPCC spokesman said they would not comment on Mr Smyth's comments.
On Tuesday Mr Hardwick gave evidence to the Home Affairs Committee during which he said video images from the G20 protests in London were "disturbing".
Ian Tomlinson's death is being investigated
He said there was a need for police to explain better so-called "distraction" techniques they are trained to use in violent confrontations, which he said was a "euphemism" for "kicking, hitting, or striking".
Mr Hardwick said the police should not have issued a statement under media pressure to say there had been no contact with newspaper seller Ian Tomlinson before he collapsed and died.
A policeman has been interviewed under caution on suspicion of manslaughter after new tests overturned the initial post-mortem examination into the cause of Mr Tomlinson's death, who was filmed being struck and pushed over.
On Tuesday it was confirmed that a third post-mortem examination will be carried out to determine the cause of death.
Meanwhile, Metropolitan Police Commissioner Sir Paul Stephenson has criticised officers who failed to display their ID numbers.
"It is absolutely unacceptable for any police officer who should have identification numbers on not to have those identification numbers on," he said.
"However, I will say there needs to be a context here. That operation was one of the most complex policing operations that's ever been undertaken - protecting multiple heads of state."
Home Office minister Lord West of Spithead told the House of Lords that thousands of officers had acted "absolutely professionally" during the G20 protests.
But the peer added: "This does not excuse acts that are criminal and there are now investigations for those particulars."