American spy chiefs have told the president that the Central Intelligence Agency
has launched a vast spying operation in Britain to prevent a repeat of the 9/11 attacks being launched from Britain, the paper said.
It said spy chiefs believe that a British-born Pakistani extremist entering the US under a current visa waiver programme for all Britons is the most likely source of another terrorist spectacular on American soil.
A former CIA officer who has advised Obama told The Sunday Telegraph that the CIA has stepped up its British operations after the November Mumbai massacre by the Lashkar-e-Taiba, which has an extensive web of supporters in Britain, and is now as big a threat to the US and Britain as the al-Qaida.
Bruce Riedel told the paper: "The British Pakistani community is recognised as probably al-Qaida's best mechanism for launching an attack against North America."
"The Americans run their own assets in the Pakistani community; they get their own intelligence. There's close cooperation with MI5 but they don't tell us the names of all their sources.
"Around 40% of CIA activity on homeland threats is now in the UK. This is quite unprecedented," he added.
Explaining the increase in CIA activity over the past month, Riedel added: "In the aftermath of the Mumbai attack the US and the UK intelligence services now have to regard Lashkar-e-Taiba as just as serious a threat to both of our countries as al-Qaeda.
"They have a much more extensive base among Pakistani diaspora communities in the UK than al-Qaida."