This policy, which was revealed through freedom of information requests by The Rendition Project, suggests ministers can approve action carrying a serious risk of torture if “the potential benefits justify accepting the risk and legal consequences”.

This policy also makes a provision for ministers to pre-approve lists of individuals about whom information may be shared.

It is in contrast to the government’s ‘official’ torture policy, known as the Consolidated Guidance, which is currently being reviewed in a public consultation by the Investigatory Powers Commissioner (IPCO) Sir Adrian Fulford.

Sir Adrian’s review was ordered after the Intelligence and Security Committee published a report revealing new details about post-9/11 UK involvement in torture and mistreatment.

IPCO confirmed to The Times that it didn’t know about the document before it was shown to them by Reprieve.

In May last year, the government gave an unprecedented public apology to Abdul-Hakim Belhaj and his wife Fatima Boudchar for British involvement in their rendition to torture. Mr Belhaj and Ms Boudchar were kidnapped by the CIA with the help of British intelligence in 2004, before being tortured in CIA custody.

The couple were subsequently rendered to Gaddafi’s Libya. In a fax discovered at the headquarters of Libyan intelligence, former MI6 head of counter-terrorism officer Sir Mark Allen congratulated spy chief Mr Koussa on the “safe arrival” of Mr Belhaj and claimed that the intelligence about Mr Belhaj “was British”.

Last month it was revealed that the government had spent £11m of public money fighting the pair’s legal challenge to obtain an apology from the government.

The government promised to announce by late August 2018 whether it would hold an independent, judge-led inquiry into UK involvement in torture, but has since missed that deadline and indicated that a final decision is currently sitting with the Prime Minister.

Reprieve deputy director Dan Dolan, said: This previously-secret document brings to mind the worst excesses of the War on Terror and tramples all over the government’s official policy. Ministers can’t authorise action leading to torture without breaking the law.