The actions of some police officers at the G20 protests were "unacceptable", according to both the Met Commissioner, Sir Paul Stephenson, and the man leading the investigation into police tactics.
Sir Paul said it was "absolutely unacceptable" that some officers covered or removed their identity shoulder tags during the protests.
Denis O'Connor, the new Chief Inspector of Constabulary, called for an immediate end to the practice. Mr O'Connor, appearing before the Commons Home Affairs Committee, contrasted alleged police brutality against protesters to the heroism shown by the south London constable Gary Toms, who died last week after he was run down by a getaway car.
"When you see something that does not square with that noble cause, it is disappointing and hugely concerning," Mr O'Connor said. "My concern was obviously about the individual incidents where officers, on the face of it, appeared to break with their colleagues and assault people."
The Home Affairs Committee confirmed that it would hold its own inquiry into the G20 policing, as The Independent disclosed yesterday. It plans to publish its report in June, alongside Mr O'Connor's initial conclusions on the tactics used by police.
Mr O'Connor admitted that seeing images of protester Nicola Fisher being struck across the face by an officer made him "very uncomfortable". He added: "I would expect police officers in public order and other situations to wear their numbers so the public can identify them. It acts as a good check and balance for all parties in the situation."
More evidence of police brutality emerged yesterday: a video posted on YouTube showed a young, female protester being pushed in the face by an officer. The Independent Police Complaints Commission (IPCC) is conducting three investigations into G20 policing, examining the death of Ian Tomlinson, the treatment of Ms Fisher and a complaint from an unnamed 23-year-old man.
Yesterday, Police Federation chairman Peter Smith accused IPCC chairman Nick Hardwick of running a witch-hunt against G20 officers and depicted him as a "grandstanding anti-police campaigner". "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," he said.
Yesterday, as more footage emerged of alleged police brutality, the IPCC failed to secure an injunction to prevent Channel 4 News from broadcasting fresh pictures of events preceding Mr Tomlinson's death. Originally intended to be screened yesterday, the report is now scheduled to be shown tonight.
The IPCC said yesterday that a third post-mortem would be carried out on Mr Tomlinson, who died minutes after being pushed to the ground by an officer. The first post-mortem concluded that he died from a heart attack, but a second examination certified the cause of death as abdominal bleeding.
Mr O'Connor admitted to concerns about the use of "kettling", a tactic deployed by police during the G20 protests to restrict the movement of protesters. It meant that some people caught up in the protests on their way home from work were prevented from leaving for many hours, while those penned in were denied access to food and drink. He said the tactic posed obvious problems when used "inflexibly", and his investigation would be examining how it was applied during the G20 summit. Tom Brake, a Liberal Democrat member of the committee, released a video showing police preventing a journalist from leaving the "kettle".
MPs also raised concerns over so-called "distraction tactics", which allow officers to strike anyone who they believe is acting violently. Nick Hardwick, head of the IPCC, said that the term was a "euphemism" and that support for the technique may have to be looked at as officers could not be blamed for deploying a tactic they had been trained to use. The Police Federation accused him of conducting a witch-hunt against G20 officers.
The Home Office minister Lord West defended G20 police. "I think we should be extremely proud of them," he said.
He did not want to "excuse" any "criminal acts" under investigation, he said, but insisted that British police tactics were better than "water cannon, baton rounds or shooting people - all of which seem to occur in some other countries".
Lord West, speaking in the House of Lords, added: "Thousands of officers acted absolutely professionally and proportionately, thousands were actually able to demonstrate peacefully on our streets, criminal activity in the rest of the metropolis was kept to an absolute minimum and the police also maintained high levels of security.
"And I think we should be extremely proud of them. This does not excuse acts which are criminal and there are now investigations taking place for those particulars.
"But in general I think we are very well-served by our police. I am very proud of them and the way I approach it generally is they are on our side and they are our people."
A policeman has been interviewed under caution on suspicion of Mr Tomlinson's manslaughter.