Liberal Democrats have backed a policy motion on policing protests.
Civil liberties arguments came to the fore during the debate this morning at the party's conference.
The motion says that "it is not the business of the police to set the boundaries of democratic expression" and "demonstrations and other peaceful forms of protest are a fundamental democratic right".
Tom Brake, MP for Carshalton and Wallington, told conference about his experiences at the G20 protests in the City of London in April.
He was among protesters detained for five hours and said he witnessed violence by protesters and the police's "proportionate" response.
However, he said it was unacceptable that water and toilets were denied to peaceful protesters.
"This must not happen again there can be no excuse for officers not displaying their ID numbers," he said.
Dee Doocey, a member of the London Assembly, said: "The police should protect our liberties and deal firmly only with genuine law breakers."
Ruth Coleman, prospective parliamentary candidate for Leeds West, claimed the Labour government has "lost faith in democracy".
"The police do not operate in a vacuum, and we have to ask what sort of society has the Labour government created," she said.
"Simply opposing government policy can get you branded a traitor."
She claimed protests have "almost vanished from our streets" and "people who dissent from government policy can find themselves treated like criminals".
Coleman said protest and dissent test the policies of the people in charge.
"I am quite sure that many police are unhappy at the way they are being used at the moment," she said.
David Howarth, Lib Dem justice spokesman, said: "The ugly scenes of police aggression and intimidation witnessed at the G20 protests and the Kingsnorth demonstrations were a national disgrace.
"Tactics like baton charges, the seizure of personal property and the kettling of protestors for hours on end are fundamentally wrong.
"They are a threat to democratic rights, they cause distress and injury, increase tension, provoke reaction and damage the reputation of the police.
"These tactics must change. The police must recognise the democratic right to protest and put the protection of the public first at all times."
The policy motion, which was overwhelmingly approved, calls the use of aggressive or intimidatory tactics against peaceful protesters "provocative, inappropriate, and counter-productive".
The police must use "aggressive tactics" such as 'kettling', baton charges, and attacks with dogs "only when they are absolutely necessary and proportionate; the seizure of personal property from demonstrators is not acceptable."
Any officers not clearly identifying themselves by wearing an identification number "are committing a disciplinary offence; this rule is unlikely to be respected unless transgressors are subject to disciplinary procedures".
