There were large-scale demonstrations at the G20 summit
The Metropolitan Police should ensure its officers are properly trained in public order policing, a report says.
This is among several recommendations made by the Metropolitan Police Authority in a report into policing at the G20 protests in London last year.
It also says disciplinary action should be taken against officers who do not display their identification numbers.
The report comes after the death of Ian Tomlinson, who was pushed over by a policeman during the demonstrations.
The Report by the MPA Civil Liberties Panel, entitled Post G20, investigated the Met's current public order policing strategies and will be presented to the full Authority for final ratification on 25 March.
The Independent Police Complaints Commission said it received at least 185 complaints about the G20 protests, some 40 of which were not eligible. More than 50 were about police tactics and more than 80 from people claiming to have seen or experienced excessive force by police officers.
The MPA report also said officers should challenge any inappropriate behaviour by their colleagues.
Other recommendations included ensuring that officer briefings at the start of operations emphasise any use of force should always be the minimum necessary to resolve a situation.
And it should be made easier for protesters to access the police, "by developing and disseminating clear guidelines on who to contact and how".
The report also suggested that police be more transparent in the communication of the policing strategies "to give the media and the public confidence that facilitating peaceful protest is a reality".
Victoria Borwick, MPA member and chair of the panel, said: "The impact on public confidence when public order policing goes wrong, even though those instances may be very rare, cannot be underestimated.
"The Civil Liberties Panel acknowledges that the Met police thousands of public order events every year, most of which pass without incident.
"But there was significant criticism and a fundamental questioning of the Met's approach to policing protest after the G20 demonstrations in central London in April 2009, followed by the tragic death of Ian Tomlinson.
"To maintain public confidence in the way protests are policed we have to find a balance between civil liberties and the need to maintain public safety and public order through proportionate policing."
Mr Tomlinson, a 47-year-old newspaper vendor, died minutes after he was pushed over by an officer during the demonstrations on 1 April.
The police officer at the centre of that allegation has been suspended and interviewed under caution on suspicion of manslaughter in connection with the death.
The report also said relationships between event organisers and the police have "clearly been damaged" as a result of the "perceived heavy handed policing of various protests and demonstrations prior to G20, not just in London and not just by the Metropolitan Police".
The Met police told the MPA they had tried to address this during the subsequent August climate camp, also held in London.