Lawyers told Britain to come clean yesterday on whether it let the US run a secret torture site on an overseas territory.

Legal action charity Reprieve has written to Foreign Secretary William Hague following reports that the CIA set up a “black site” on Diego Garcia.

Al-Jazeera said this week that a secret US Senate intelligence committee report found “that the CIA detained some high-value suspects on Diego Garcia, an Indian Ocean island controlled by the United Kingdom and leased to the United States.”

And classified CIA documents showed it was run with Britain’s “full co-operation.”

After repeated denials the government finally admitted in 2008 that two rendition flights carrying detainees refuelled on Diego Garcia in 2002.

But it continues to deny that any prisoners were held that or that that a secret CIA prison existed.

Reprieve said that in 2004 anti-Gaddafi militant Abdulhakim Belhadj and his wife were rendered back to Libya in a joint CIA-MI6 operation and, according to a CIA flight plan found following the toppling of Gaddafi, were scheduled to be flown via Diego Garcia.

But in December 2011 Foreign Minister David Lidington told Parliament: “No flights with a detainee on board landed on Diego Garcia in March 2004.”

He added that, apart from the two cases in 2002, the US government had confirmed no other US intelligence flights had landed “in the UK, our overseas territories or the crown dependencies with a detainee on board since September 11 2001.”

Reprieve director Cori Crider said: “We need to know immediately whether ministers misled Parliament over CIA torture on British soil.

“If the CIA operated a black site on Diego Garcia then a string of official statements — from both this and the last government — were totally false.

“Were ministers asleep at the wheel or, as the report suggests, have we been lied to for years?”

When asked for comment, a Foreign Office spokeswoman referred the Star to the department’s previous statements.