However, in an official briefing, the Prime Minister’s spokesman said that British intelligence was shared with the Americans.
He said: “Clearly there was security information about this individual’s activities and that was information that was shared with the US authorities. That is the key point.”
The spokesman added: “We are pretty certain that he was radicalised outside the UK. He [Abdulmutallab] left the UK in October 2008.
“But it is also clear that while he was here he was attempting to make contact with people and that is the intelligence we were able to secure from the intelligence services.”
Last night, a Downing Street spokesman added: "We do routinely share large quantites of intelligence with the US on a two-way basis so we can build up a picture of the potential threats we face.
In regard to the Detroit bomber, the UK and US had gathered partial information and this had been shared in the usual way. Since the incident, we have built up a fuller picture.
http://www.telegraph.co.uk/news/uknews/terrorism-in-the-uk/6933707/MI5-told-US-about-Detroit-bombers-terror-links-a-year-ago.html