Fresh claims about British security service collusion in torture were abruptly silenced today by a parliamentary committee, amid claims that if made public they would cut across an ongoing legal case.

Clive Stafford Smith, director of the human rights group Reprieve, was due to make detailed claims to the Commons foreign affairs committee about Binyam Mohamed, the UK resident who says British security officers colluded in his torture, and about America's use of the British territory of Diego Garcia to secretly render terror suspects.

But the cross-party committee cancelled the session at the last minute, issuing a statement from Mike Gapes, the committee's Labour chairman, who said he had received advice that the cases due to be raised fell "wholly within the house sub judice resolution".

That resolution states that "cases in which proceedings are active in United Kingdom courts shall not be referred to in any motion, debate or question", Gapes said. Mohamed's treatment before he was flown to Guant?namo Bay is the subject of a police investigation into "possible criminal wrongdoing" by an MI5 officer.

It is also the subject of a bitter high court row about the government's refusal to disclose CIA information about Mohamed's treatment. In a letter to Gordon Brown yesterday, lawyer Stafford Smith said that a British informant told London about Mohamed's imprisonment in Morocco where he says he was tortured. British authorities have said they did not know he was being held in Morocco until later.