LONDON, Feb 17: A policy governing the interrogation of terrorism suspects in Pakistan that led to British citizens and residents being tortured was devised by MI5 lawyers and figures in government, according to evidence heard in court.

A report in Guardian on Tuesday said a number of British terrorism suspects who had been detained without trial in Pakistan said they were tortured by Pakistani intelligence agents before being questioned by MI5. In some cases their accusations are supported by medical evidence.

The existence of an official interrogation policy emerged during cross-examination in the high court in London of an MI5 officer who had questioned one of the detainees, Binyam Mohamed, the British resident currently held in Guantánamo Bay.

The officer, who can be identified only as Witness B, admitted that although Mohamed had been in Pakistani custody for five weeks, and he knew the country to have a poor human rights record, he did not ask whether he had been tortured or mistreated, did not inquire why he had lost weight, and did not consider whether his detention without trial was illegal.

Mohamed is expected to return to Britain soon after ending a five-week hunger strike at Guantánamo Bay, where he was being force-fed. After he was seen by British officials and a doctor over the weekend, the Foreign Office said he was medically fit to travel.

Cross-examined in the high court last year, Witness B acknowledged that Mohamed was in “an extremely vulnerable position” when he questioned him in Karachi in 2002. The MI5 officer admitted telling him that “he would get more lenient treatment if he cooperated”, and said that he knew he was to be transferred to US custody.

Witness B was asked by Dinah Rose: “Was it your understanding that it was lawful for Mr Mohamed to be transferred to the US authorities in this way?” Witness B replied: “I consider that to be a matter for the security service top management and for government.”

Asked then whether the transfer concerned him, Witness B replied: “I was aware that the general question of interviewing detainees had been discussed at length by security service management legal advisers and government, and I acted in this case, as in others, under the strong impression that it was considered to be proper and lawful.”

He denied that he had threatened Mohamed and said the prisoner appeared well enough to be questioned.

Mohamed was eventually able to tell lawyers that before being questioned by MI5 he had been hung from leather straps, beaten and threatened with a firearm by Pakistani intelligence officers. After the meeting with MI5 he was “rendered” to Morocco where he endured 18 months of even more brutal torture, including having his genitals slashed with a scalpel. Some of the questions put to him under torture in Morocco were based on information passed by MI5 to the US.

The Guardian has learned from other sources that the interrogation policy was directed at a high level within Whitehall and that it has been further developed since Mohamed’s detention in Pakistan. Evidence of this might emerge from 42 undisclosed US documents seen by the high court and sent to the MPs and peers on the intelligence and security committee (ISC).