NO JUSTICE: A protester holds up a picture of Shaker Aamer, who has been in Guantanamo Bay for eight years

Up to 20 Britons may have been tortured abroad with the complicity of the government and MI5, a human rights watchdog has revealed.

The Equality and Human Rights Commission has called for an "urgent review" into allegations that Britain was complicit in the torture of more than 20 Britons including high profile cases such as those of Binyam Mohamed and Shaker Aamer.

Equality and Human Rights Commission chairman Trevor Phillips said: "Ministers and government agencies are facing very serious allegations of knowing that UK citizens were being tortured, failing to take action to stop that torture and supplying questions to be used in the interrogation of men who were subjected to a high level of ill-treatment.

"Given the UK's role as a world leader on human rights, it would be inexplicable for the government not to urgently put in place an independent review process to assess the truth, or otherwise, of these allegations."

The allegations have added to the intense pressure on the government to establish a full public inquiry into the state's role in the kidnap and torture of its own citizens and residents.

An influential committee of MPs called this weekend for the publication of the government's guidance to the security services on interrogation practices and also demanded a public investigation into the allegations of torture.

On Friday, the Metropolitan Police formally approached the courts to request secret documents relating to the alleged complicity of MI5 in the torture of British resident Shaker Aamer.

The request is an extension of the Met's ongoing investigation into the alleged role of an MI5 agent, known as Witness B, in the torture of Binyam Mohamed.

Mr Aamer, a Saudi national with British residency, has been held without charge for eight years and remains imprisoned in Guantanamo Bay.

Amnesty International UK counter-terrorism campaigner Sara Mac Neice said: "The Met's investigation into possible UK complicity in Shaker Aamer's torture is vital - just as it is with Binyam Mohamed.

"What is still needed, of course, is an independent and wide-ranging inquiry into all aspects of the UK's alleged involvement in human rights abuses like rendition, secret detention and torture.

"It's an absolute disgrace that Shaker Aamer has been held without charge or trial for eight years at Guantánamo and it's now imperative that the UK government starts to make real efforts to secure his release."

The government is currently embroiled in a number of legal actions and has suffered a string of humiliating defeats in the courts in recent months.

Despite seemingly incontrovertible evidence of British complicity in the tortue of Mr Mohamed, Mr Aamer and others and a damning criticism of the behaviour of the intelligence services by one of the country's most senior judges this month, both the government and MI5 continue to deny any wrongdoing.