Mr Mohamed, a British resident, claims he was tortured in US custody
The US government should urgently release details about the treatment of a British resident who alleges he was tortured, a senior Labour MP has said.
Mike Gapes, chairman of the Foreign Affairs Select Committee, said America must reveal information about former Guantanamo Bay detainee Binyam Mohamed.
Mr Mohamed, who arrived back in the UK on Monday, says he was tortured by US agents who suspected him of terrorism.
His legal team said he was now resting at a house in the countryside.
Mr Mohamed, 30, flew to Britain after being released from the Guantanamo Bay detention camp in Cuba where he had spent more than four years.
The US authorities had accused him of involvement in a plot to detonate a "dirty bomb" on American soil, but the charges were dropped last October.
Ethiopian-born Mr Mohamed claims he was tortured into falsely confessing to terrorism and alleges UK MI5 officers were complicit in his abuse.
The UK attorney general is currently consulting the director of public prosecutions over whether to order a criminal investigation into the claims.
Mr Gapes told BBC Radio 4's Today programme that the British government should be congratulated for working to secure Mr Mohamed's release.
But he said there must now be greater openness about his case to prevent long-term damage to the government and in particular, the reputation of the Foreign Secretary David Miliband.
Mr Miliband has been accused by two senior judges of bowing to pressure from the US government to keep details of Mr Mohamed's treatment secret.
"I think the solution here is that the US authorities release that information," Mr Gapes said.
"I think it is in the public interest... and this information will probably be leaked out at some point or another anyway.
"I think it's more damaging if this issue drags on - drip, drip, drip, drip, drip.
"Let's get it into the open, let's also get the attorney general's report very quickly on whether or not there is a case for legal action against someone working for the British authorities."
Mr Gapes said Mr Mohamed had made some "very serious allegations" about torture - and UK's role in it - which must be investigated.
"Our government policy, our national policy, is total opposition to torture, or complicity or collaboration in torture," he said.
"This, if it's true, is a very serious stain upon the position that consistently the government has been taking, both publicly and privately, that we do not collaborate or carry out or practice torture."
Foreign Secretary David Miliband issued a written statement on the case to the Commons on Tuesday, saying that any decision on the disclosure of further details lay with the US authorities.
"The government abhors torture and does not order or condone it," he said.
"We have raised with the US allegations of mistreatment put to us by UK nationals or residents currently or formerly detained at Guantanamo Bay, including Mr Mohamed."
Kat O'Shea, from legal charity Reprieve which represented Mr Mohamed, told the BBC News website he was still weak from a hunger strike earlier this year and was recovering at a house in the countryside.
Keith Vaz, chairman of the Home Affairs Select Committee, criticised the length of time the attorney general was taking to reach a decision about the case.
"She has access to the finest legal brains in Britain, including her own, and to take four months to make a decision of this kind is a very long time," he said. "I think we need a decision now."
The BBC's security correspondent Gordon Corera said it was clear that the High Court judges did believe Mr Mohamed had suffered some mistreatment, but it was difficult to get to the truth because of the secrecy involved in intelligence sharing between Britain and the US.
Mr Mohamed arrived back at RAF Northolt in London on Monday
But our correspondent said court judgements did show there had been a transfer of information from the UK to America concerning Mr Mohamed's case.
Mr Mohamed was released on Monday afternoon after he landed at RAF Northolt in London and underwent questioning by police.
He was held in captivity for a total of seven years - four of them in Guantanamo - after being arrested in Pakistan in 2002. He had lived in the UK from the age of 15.
Mr Miliband said Mr Mohamed's immigration status was being reviewed and allowing him to return to Britain did not constitute a commitment to giving him permanent residence status.
The foreign secretary also reiterated Britain's request for another former UK resident, Shaker Aamer, to be released from Guantanamo.