London:
American spy agency CIA warned its British counterpart MI6 that al-Qaeda was planning a "Mumbai-style" terror attack 18 months ago in the UK, but withheld detailed information because of fears that its secret sources would be exposed, a media report has said.
The CIA warned MI6 that al-Qaeda was planning an attack but withheld detailed information because of concerns it would be released by British courts, the Daily Telegraph reported. British intelligence agencies were subsequently forced to carry out their own investigations, the report quoted its sources as saying. Several potential terrorists were identified with links to a wider European plot, but it is still not known whether the UK authorities have uncovered the full extent of the threat, it said.
The breakdown in relations came after the release of US intelligence in the case of Binyam Mohamed, a former Guantanamo Bay detainee who took legal action over his incarceration, the Telegraph added.
The UK government was subsequently forced to pay millions in compensation to him and other detainees, it said. Conservative ministers are proposing establishing a system of "secret justice" to allow sensitive intelligence to be heard in British courts behind closed doors, but are facing mounting opposition from the Liberal Democrats.
Nick Clegg, the Deputy Prime Minister and Liberal Democrat leader, has written to the National Security Council and warned that the security services "cannot be allowed to ride roughshod over the principle of open justice", it said. Kenneth Clarke, the Justice Secretary, had warned that unless judges were allowed to hear evidence from MI5 and MI6 officers behind closed doors, lives would be put at risk. He said: "The Americans have got nervous that we are going to start revealing some of their information, and they have started cutting back on what they disclose.
"I'd love open justice but let's have some common sense here. Open justice cannot be at the expense of lives being lost," It is understood that details about the identity of intelligence sources and other sensitive information is no longer shared by the CIA.
The issue was raised by President Barack Obama's security advisers with their Downing Street counterparts during David Cameron's visit to Washington last month.
MI6 was said to have been particularly "frustrated" after receiving "only the tip, not the intelligence" about a plot in which armed terrorists dressed as civilians were planning to mount an indiscriminate attack on British soil.
The plot echoed an attack by extremists in Mumbai in 2008, which led to the deaths of 166 people. The CIA is also understood to have retrieved substantial intelligence about potential threats to Britain from documents seized during the raid on Osama bin Laden's compound in Pakistan.