The Prime Minister's spokesman had indicated that Umar Farouk Abdulmutallab was named in a file of people based in Britain who had made contact with radical Muslim preachers. The file was said to have been sent to the US authorities in 2008.

However, White House sources disputed the Downing Street account, stating that it was "a mistake" and no such intelligence information was passed by Britain before the attempted Christmas Day attacks. The White House declined to respond officially.

The news comes as Barack Obama prepares to unveil plans aimed at thwarting future attacks as he seeks to limit political fallout from the incident.

He will outline an initial series of changes, including enhancements to the much-criticised "watchlists" of terrorism suspects, after he meets with intelligence chiefs and other top security advisers on Tuesday, first full day back from his Hawaii vacation, an administration official said.

The implication that the US failed to act could embarrass President Barack Obama, who is already under pressure after failures by US intelligence to identify the bomber.

A British official also backed claims that there appeared to have been a misunderstanding about what Downing Street had said: "There is nothing to stand up the suggestion that the UK provided information to the US that it could or should have acted upon."

Diplomatic sources said that the Prime Minister's spokesman had intended to refer to information gleaned by MI5 after the Christmas Day incident following an exhaustive examination of records going back through Abdulmutallab's time in Britain up to October 2008.

It could also add to concern over the state of the "special relationship" between Downing Street and the White House following last year's dispute over the early release of the Lockerbie bomber.

It is extremely unusual for the Prime Minister's office to comment on intelligence matters. The move could be seen as an attempt to rebuff criticism from senior American figures who claimed that Britain had nurtured Islamic extremism.

At first it was thought that MI5 gathered only limited information on Abdulmutallab and had therefore not alerted the US.

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 quantities 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.

There is no suggestion that the US did not act on intelligence information that they received from the UK."

Questions will be asked about how much MI5 knew about Abdulmutallab and whether the information was correctly handled. Sources said he was given the attention he warranted at the time, and the fact that he associated with other extremists in this country was not surprising.

Abdulmutallab, a Nigerian, studied at University College London between 2005 and 2008. He then left the country and was thought to have travelled to Yemen.

He attempted to detonate a bomb hidden in his underwear on Northwest Airlines flight 253 to Detroit on Christmas Day.

The decision by Downing Street to give details of the shared intelligence was unlikely to be welcomed by the White House. It was the latest in a series of incidents, which have strained relations between Britain and America.

Last summer, the Americans were angered by the decision of the Scottish administration to release the Lockerbie bomber on compassionate grounds. In September, Mr Obama rebuffed five requests for a private meeting with the Prime Minister when he visited New York.

At the weekend, the Prime Minister announced a British-US initiative to tackle terrorism in Yemen. The White House then made it clear that Mr Brown had not spoken to President Obama since the Detroit bomber was apprehended. The Prime Minister was then forced to admit that it was an old programme.

Last week, it was found that the bomber had come to the attention of MI5 when he made contact with a number of individuals who were under surveillance. However, MI5 was not thought to have identified Abdulmutallab as a threat and he was not fully investigated. The bomber was therefore not placed on international watch lists and was able to board a plane from Nigeria to America, via Amsterdam last month.

Although he appeared in a number of top secret intelligence reports, Abdulmutallab was allowed to keep his American visa.

Abdulmutallab's father contacted the CIA in November to give them warning that his son was involved with fundamentalists in Yemen.

Communications were intercepted in Yemen, which referred to a possible attack by "the Nigerian". American intelligence experts have criticised the failure to identify the potential threat and drawn comparisons with 2001, when the CIA and FBI missed warning signs of the September 11 attacks.