Farid Hilali was extradited from Britain to Spain in 2008
Police are investigating a report from a human rights group alleging UK involvement in the torture of British terror suspects abroad.
Cageprisoners - which campaigns on terror detention - said there were 29 cases of security service involvement with tortured or mistreated suspects.
One case cited, of Moroccan-born Farid Hilali, pre-dates the 9/11 attacks.
UK authorities deny collusion but say interrogating suspects in foreign prisons yields valuable intelligence.
A Metropolitan Police spokesman said the force had received the 55-page Fabricating Terrorism II dossier on Friday.
"We have received a report and are considering its contents," he said.
Responding to the latest claims from Cageprisoners the UK Foreign and Commonwealth Office (FCO) said it took any allegations of mistreatment or torture "seriously".
"The UK's position on torture is clear. We abhor torture. We don't participate, solicit, encourage or condone it. We unreservedly condemn extraordinary rendition for torture," said a statement.
'War on terror'
The allegations include rendition - where suspects are moved between countries for questioning - and interrogation of suspects by MI5, MI6 and the SAS in foreign prisons where they have been tortured or otherwise mistreated.
All of the alleged mistreatment took place abroad and the Cageprisoners report lists a number of countries including Afghanistan, Pakistan, Egypt, Syria, Jordan, Morocco, the United Arab Emirates and Kenya.
A number of those making allegations were transferred to and then released from Guantanamo Bay, while others are serving prison sentences in Britain for terrorism offences.
Farid Hilali, a Moroccan man who had been living in Britain, has said he was questioned by British intelligence officers in a prison in the United Arab Emirates, where he was tortured.
The claims go back to 1999, two years before the terrorist attacks in New York, Washington and Pennsylvania, after which US President George Bush launched what he called the "war on terror".
Mr Hilali was subsequently arrested again in Britain in 2003, detained on immigration offences, and later accused of having links to the 9/11 attacks.
He was extradited to Spain in 2008 after authorities there alleged he was party to a conspiracy there that was linked to and supportive of the terrorist attacks in 2001.
'Strongest claims yet'
The case of Binyam Mohammed, who returned to the UK from Guantanamo Bay this year, brought allegations of British involvement in the torture of terrorism suspects to the fore.
However, the claims have been around for some years, said BBC home affairs correspondent Daniel Sandford.
The latest allegations were the "strongest yet", he added.
Last month police said they would investigate whether an MI5 officer was complicit in the torture of Mr Mohamed, 30, who was born in Ethiopia and moved to Britain aged 15.
Mr Mohamed, a British resident, claims he was tortured in US custody
Mr Mohamed says he was tortured while in US custody in Pakistan, Morocco and Afghanistan, with the complicity of MI5.
Mr Mohamed said MI5 had prolonged his detention and torture while he was being held in Morocco in 2002.
The MI5 agent who questioned him has denied threatening or putting any pressure on Mr Mohamed.
The Attorney General, Baroness Scotland QC, said the police probe was "the appropriate course of action".
BBC security correspondent Frank Gardner said it was the first time anyone could remember the police being asked to investigate MI5.
Following the latest allegations the FCO added that it expected all countries to abide by international law including the UN convention against torture and the EU convention on human rights, as Britain did.
"It is our longstanding policy not to comment on any operational work of the intelligence services, however if there was any question of any person acting in an official capacity being involved in an act of torture then this would be a matter for the police," they said.