Two terror suspects who were flown by the CIA to the British territory of Diego Garcia and later allegedly tortured have been named and evidence about their treatment has been revealed for the first time. Mohammed Madni and Shaykh al-Libi are identified in evidence prepared for the Commons foreign affairs committee by Clive Stafford Smith, director of the human rights group Reprieve.

They are the two men, said Stafford Smith, referred to, but not identified, by David Miliband, the foreign secretary, when last year, after repeated denials by ministers, he admitted that two people had been rendered through the island in the Indian Ocean in 2002. Miliband said he did not know who the men were.

Stafford Smith said detailed research showed that Madni, who holds dual Pakistani-Egyptian nationality, was rendered through Diego Garcia in January 2002. He was subsequently jailed and interrogated in Egypt and flown to Guantánamo.

Madni was later freed and returned to Pakistan where Reprieve's lawyers met him. "He has been effectively crippled by his torture," said Stafford Smith.

The other man rendered through the US base on the island was likely to be Libi, he added. While questioned in Egypt, Libi claimed that al-Qaida was in league with Saddam Hussein, a claim now accepted by the US to be false. He was recently freed and died in Libya two weeks ago.

Stafford Smith was due to present his evidence on Diego Garcia to the foreign affairs committee last week but was prevented from doing so on the grounds that the other issue he was expected to testify on – the treatment of Binyam Mohammed, the UK resident who was jailed in Pakistan, Morocco and Afghanistan, before being flown to Guantánamo – was sub judice.

Mike Gapes, the committee's Labour chairman, said he had received advice that the cases due to be raised fell "wholly within the house sub judice resolution". The resolution states that "cases in which proceedings are active in UK courts shall not be referred to in any motion, debate or question". Mohammed's treatment before he was flown to Guantánamo is the subject of a police investigation into "possible criminal wrongdoing" by the CIA and an MI5 officer.

Stafford Smith said the advice was wrong and that the Mohammed case had been frequently raised in the Commons and the Lords. "It is time for the UK government to come clean about its role in Madni's detention and to reveal who else has been held on and rendered through Diego Garcia, what happened to them there, and where they are now," he said.

Edward Davey, the Liberal Democrat foreign affairs spokesman, said last night: "These astonishing allegations fly in the face of the assurances given by the foreign secretary to parliament. The use of British territory for illegal state abduction and detention is unacceptable". Research by his party found that the government had systematically destroyed flight logs for the Diego Garcia US airbase, Davey added.