Police risk losing public confidence if they do not change how they manage protests, the police watchdog said today.
Her Majesty's Chief Inspector of Constabulary, Denis O'Connor, said senior officers were too focused on dealing with disorder, and not enough on allowing peaceful protest.
Public order training and tactics were "inadequate for the modern day", he said, in his review of the G20 protests in central London on 1 April.
The report found officers were too interested in whether protests were lawful or not, instead of focusing on allowing peaceful demonstrations.
Some officers policing G20 were not sufficiently aware of human rights laws, he said, and he criticised police use of containment to pen in demonstrators on the day Ian Tomlinson died, calling it "inconsistent".
Mr O'Connor called on the Association of Chief Police Officers (Acpo) to carry out a wide-ranging review of tactics and training for officers dealing with protesters.
The review should include a medical assessment of the damage done by shields and batons carried by riot police, he said.
In future, containment should be used more flexibly, and vulnerable or distressed people should be allowed out, he said.
Mr O'Connor said the changes needed to be made as soon as possible to "meet the challenges of the 21st century", and would be especially important for the Olympic Games in 2012.
He said: "If these recommendations are not adopted, then I would expect there would be more disruption in our lives potentially.
"There will be more very problematic incidents, and police will be challenged in court, and I think the public will become progressively aware of it and consent will be withdrawn.
"It won't necessarily be a cliff-face, but it will be another sad erosion of the faith in British policing."
The report backed the continued use of containment techniques known as "kettling".
Mr O'Connor said they were useful in preventing "running riots", but he said they needed to be tempered, and officers needed to watch the crowds for signs of anyone in distress.
He added: "What the review identifies is that the world is changing, and the police need to think about changing their approach to policing protest.
"We live in an age where public consent of policing cannot be assumed, and policing, including public order policing, should be designed to win the consent of the public.
"Future events, like the 2012 Olympics, make change all the more critical."Reuse content