The practice of holding people in one place for long periods, widely known as “kettling”, cannot always be justified, a committee of MPs found.

Members of the Commons Home Affairs Committee said it is not acceptable to impose a blanket ban on movement – and that peaceful protesters should be allowed to leave.

They said frontline officers must be given discretion to allow some people to escape highly-charged events.

The findings were contained in a report published by the committee into the G20 protests in the City of London.

More than 35,000 people took to the streets as world leaders met over two days at the beginning of April.

The police have endured a barrage of criticism in the aftermath of the death of newspaper seller Ian Tomlinson, who was pushed to the ground during clashes.

Independent investigators have launched several inquiries after evidence of police officers lashing out at protesters was caught on camera.

The Home Affairs Committee report said a small number of high-profile incidents could damage the confidence of the public in police.