Leaks that revealed British agent's role in foiled bomb plot investigated by FBI

Consternation grew on both sides of the Atlantic yesterday at leaks in the US media over the foiled al-Qa'ida bomb plot – the latest of them that the key infiltrator into the terrorist organisation's Yemen network was a British citizen apparently of Saudi origin who was recruited, according to some accounts, by MI5.

The leaks, beginning with an Associated Press report on Monday the news agency had held back for several days at the request of the US authorities, have turned the spotlight on a spectacularly successful co-operation between the intelligence services of the US, Saudi Arabia and Britain.

But senior officials and analysts in Washington and London have warned that exposure of the affair will further increase al-Qa'ida's wariness, and make it even harder to find potential moles ready to risk their lives in such operations. To counter al-Qa'ida, "you have to protect your agents, and you have to protect the confidence" that foreign intelligence services have when they collaborate with the CIA, said the US Secretary of Defence Leon Panetta.

At least two investigations are under way into the source of the leak, one ordered by James Clapper, the director of National Intelligence and the other led by the FBI.

"Such a small universe of people knew about it. No one in Congress at all," Mr King said. "I'm not aware of any other intelligence operation that was so closely held as this. We're talking about life and death here."

But the anger here is matched by that in London, where the US is again accused of being congenitally unable to keep a secret. If the disclosure was not deliberate, said Patrick Mercer, the Tory MP and former shadow security minister, "it is a shocking example of a leak posing risks to highly important work".

This is not the first time such intelligence leaks have occurred here, but even by Washington's porous standards this one is unusual, both it its detail and its closeness to the event itself.

The operation, targeting the Yemeni bomb maker Ibrahim Hassan al-Asiri, had been under way for several months, before the mole, posing as a volunteer suicide bomber, managed to pass to western intelligence the device he was supposed to smuggle aboard a US-bound flight and detonate. AP only published its story about the failed plot after the drone strike on Sunday in Yemen that killed Fahd al-Quso, a top operative of al-Qa'ida in the Arabian peninsula.

That attack was apparently on the basis of information provided by the infiltrant, now in hiding. Then it emerged that a "double agent" was involved, and now that he was a British passport holder of Saudi origin.