A woman looks on as police is preventing G20 demonstrators from leaving the Bank of England area in a controversial tactic known as kettling. Photograph: Andrew Otto.

The Government today defended the controversial police tactic of “kettling”, whereby large number of protestors are herded into a closed-off area and prevented from leaving, saying demonstrators might otherwise cause massive destruction.

But minister of state in charge of policing, Vernon Coaker said the ongoing review of police tactics, called after the G20 summit in April, should consider allowing individual peaceful protestors to leave. Mr Coaker added that the police may have to consider, where possible, giving water and medical attention to locked up protesters.

Kettling was used at the Bank of England during the G20 protests, leaving hundreds of demonstrators, many of them entirely peaceful, stranded for as long as seven hours. Bank Tube station was subsequently turned into a public lavatory as people were not allowed to cross the police line.

Mr Coaker said kettling should still be available as a tactic to police commanders on the ground, calling it a useful action that can help stop violent protests from spreading.

Courts had previously upheld the right of police to kettling as long as the tactic was used in good faith, proportionately, and was enforced for no longer than was reasonably necessary.

The director of Liberty (The National Council for Civil Liberties), Shami Chakrabarti, had told the BBC that she had serious concerns about kettling in difficult situations. “Imprisoning them in this way risks making people angry, making them desperate and exacerbating any risk to public safety,” she said.

The Met Police Commissioner had ordered a review into kettling after it attracted controversy at April’s G20 demonstrations. The review, conducted by HM Inspectorate of Constabulary, is considering whether it is used too often and whether police officers used appropriate force to impose the containment.