Police tactics of containing thousands of people for several hours at the Bank of England protests and using batons against climate camp protesters were condemned yesterday as an infringement of the right to demonstrate.

In the aftermath of the G20 protests in the City of London, politicians, demonstrators and a former police officer raised concerns about the methods used by the Metropolitan police to control crowds of more than 5,000.

Eyewitnesses said hundreds of environmental demonstrators camping out along Bishopsgate in a peaceful protest during the day were cleared from the area aggressively by riot police with batons and dogs after nightfall on Wednesday.

The police had earlier said they would ask the protesters, whom they acknowledged were peaceful, to move as night fell. Commander Simon O'Brien, said his officers would be "politely and proportionately" asking campers to move on.

But one eyewitness, Martin Horwood, the Liberal Democrat MP for Cheltenham, said dogs were used on protesters near the camp. James Lloyd, a legal adviser in the camp, said riot police forcefully cleared the area using batons around midnight.

"There was no announcement, the riot police just started moving forward very quickly from the south," he said. "They were pushing everyone back, pushing forward quickly. They caused panic, people were screaming and shouting ... There was a person in a wheelchair struggling to move, being pushed forcibly by them. It was totally disproportionate."

Another eyewitness, Ashley Parsons, said: "The violence perpetrated against so many around me over that hour was sickening and terrifying.

"Without warning, from around midnight, the police repeatedly and violently surged forwards in full riot gear, occasionally rampaging through the protest line and deliberately destroying protesters' property, some officers openly screaming in pumped-up rage."

Outside the Bank of England, thousands were held for up to eight hours behind a police cordon, in a practice known as "kettling". Parents with children and passers-by were told by officers on the cordon that "no one could leave".

According to witnesses, when they were finally allowed to go on Wednesday night, they were ordered to provide names and addresses and have their pictures taken. If they refused, they were sent back behind the cordon.

John O'Connor, a former Met officer, criticised the tactic. "They are using this more and more," he said. "Instead of sending snatch squads in to remove those in the crowd who are committing criminal offences, they contain everyone for hours. It is a retrograde step ... it is an infringement of civil liberties."

The tactic was challenged in the courts by two demonstrators who were held for seven hours at Oxford Circus, central London, during the May Day protests in 2001. They claimed their imprisonment breached their rights to liberty but a House of Lords judgment ruled the tactics legal.

Senior police defended their actions, saying they were dealing with a small minority bent on violence, while allowing the demonstrations to go ahead.

They said the investigations were continuing. Two squats in east London were raided yesterday after officers viewed video footage taken by special teams. By last night the number arrested rose to 122 over three days. Four people were charged with damage to a branch of the Royal Bank of Scotland on Wednesday. Mindaugas Lenartavicius, 21, was charged with arson recklessly endangering life, Daniel Champion and Ben Shiells, both 18, with burglary, criminal damage and theft of a computer, and a 17-year-old girl with burglary with intent to cause damage.

O'Brien said the cordons were put in place because a group of about 200 people were violent. "There was no real deliberate attempt to say you are all going to stay here for hours," he said.

He said people had been allowed to leave throughout the day, and that by about 7.30pm those left were people who wanted to be there, and they were asked for their names as they left as part of the inquiry. "What I saw there at that time was a couple of hundred people who did not want to go. They had ... been the agitators throughout the day," he said.

The Guardian saw and spoke to many people who were clearly not agitators, but who were refused permission to leave.

David Howarth, the Liberal Democrat justice spokesman, said: "How did the police end up in a situation where they used the same degree of force on the most peaceful demonstration as they did for a violent protest at the Bank of England? They seem to only have one trick."