"Every officer is accountable under law and fully aware of the scrutiny that their actions can be held open to," London police said in a statement. "The decision to use force is made by the individual police officer, and they must account for that."

Police said the officer was a member of the Territorial Support Group, a team specialized in maintaining order at public events and dealing with potential violence.

The video footage in question allegedly shows the officer slapping a woman who was taking part in anti-G20 demonstration in front of the Bank of England on April 2. He also appears to have hit her in the legs with his baton after she complained.

Shami Chakrabarti, director of the civil rights campaign group Liberty, told reporters she found it difficult to understand "a gargantuan police officer assaulting a small woman for having the audacity to complain."

Police to review tactics

Earlier this month, another officer was suspended for allegedly pushing newspaper vendor Ian Tomlinson, who was not taking part in the protests, to the ground. Tomlinson then died of a heart attack in a nearby street.

British police also said on Wednesday that they would review the tactics employed at the G20 summit, particularly the strategy of confining demonstrators to specific small areas.

"A number of complaints have been raised in relation to the tactic of containment and as to whether this achieves that balance," the head of Scotland Yard, Paul Stephenson, told reporters. "I want to be reassured that the use of this tactic remains appropriate and proportionate."

Civil liberties groups and the opposition Liberal Democrats have called for a full-blown inquiry into the police's conduct during the summit.