Six British police officers have been accused of subjecting suspects to waterboarding, a simulated drowning tactic condemned by US President Barack Obama as torture, according to newspapers, yesterday.

The Daily Mail said the officers were alleged to have subjected four suspects to the technique during drugs raids last year, and also repeatedly dunked their heads in buckets of water.

The Times also reported the claims.

A police spokesman refused to confirm the reports but said that "very serious allegations" had been made against six officers following a drugs operation in the north London borough of Enfield on November 4, 2008.

The officers are among eight suspended earlier this year after allegations of mishandling of property during the operation, said the spokesman for London's Metropolitan Police.

It was during an inquiry into those allegations that a police employee raised new concerns about their conduct, which the spokesman said were "very serious" and had now been referred to the police watchdog.

"These are serious allegations that do raise real concern. The Met does not tolerate conduct which falls below the standards that the public and the many outstanding Met officers and staff expect," the force said in a statement.

"Any allegations of such behaviour are treated very seriously, as this case illustrates, and if found true the strongest possible action will be taken."

The Independent Police Complaints Commission confirmed it was investigating allegations against officers involved in November's raids.

The Metropolitan Police is already under fire for heavy handed tactics after receiving a stream of complaints about the way it policed the protests against the G20 meeting in London in April, during which one man died.