New video has emerged of police using force against protesters at the G20 summit of world leaders in the City of London.

The footage, filmed by an official legal observer and obtained by Sky News, shows officers in riot gear attempting to break up the makeshift climate camp at Bishopsgate on the evening of April 1, the main day of the summit.

One officer is shown using his shield repeatedly to hit at demonstrators sitting in the middle of the road. The officer next to him is seen hitting first with his shield, then leaning down towards the seated protesters and striking out with his fist.

The organisers of the climate camp say they are preparing to lodge a judicial review of Scotland Yard's actions.

In particular, Bindmans, the City law firm acting for the protesters, wants the police legally to justify the controversial practice of "kettling" - drawing a security cordon around a potential flashpoint and holding everyone inside captive for hours on end.

Protesters at the climate camp that night say they were held for more than four hours, before officers violently cleared the road.

"The footage is clearly painting a picture where this isn't bad apples, this isn't just isolated incidents, it is a systematic use of disproportionate force that looks like it has been authorised from above," said one protester.

The footage contrasts with the carnival atmosphere at the makeshift tented camp earlier the same day, when protesters danced, sang and cooked hot food, and celebrities including Vivienne Westwood, the designer, mingled with the crowd.

Bindmans has offered to make the footage available to the Independent Police Complaints Commission, which is investigating four allegations of police violence at the G20.

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