“An investigation is ongoing,” a police statement said.
It is not clear where the torture may have taken place, but a parliamentary report in July that looked into allegations of British complicity in torture listed possible cases in Pakistan, at Guantanamo Bay, in Uzbekistan and in Egypt.
The police said the case under investigation did not relate to Binyam Mohamed, a British resident who was detained in Pakistan in 2002 before being transferred to the US prison camp in Guantanamo Bay and has accused Britain of complicity in his torture in Pakistan.
The latest referral means there are now two cases involving allegations that British agents were complicit in torture abroad being investigated by the police.
The Foreign Ministry, which oversees MI6, issued a statement saying that it condemned torture and hoped that the police would carry out a full investigation.
“This case was referred to the attorney general by SIS on its own initiative, unprompted by any accusation against the service or the individual concerned,” Foreign Secretary David Miliband said in a letter posted on the ministry’s website.
Human rights organisations have accused the government of trying to cover up its involvement in the transfer of terrorism suspects to third countries where they may be subjected to torture in order to extract information from them.
The government at first denied that it had anything to with rendition the illegal movement of people to third countries without charge or any knowledge of torture, but it has since accepted that it was involved in rendition.
The referral of the latest case follows a letter written by William Hague, the opposition Conservative spokesman on foreign affairs, asking Miliband whether any British agents were complicit in torture abroad.
He wrote to Miliband following July’s report by parliament’s human rights committee, which documented a range of allegations of British complicity in torture, particularly in Pakistan.