The report provoked outrage from Democrats and Republicans on Capitol Hill.

In a sign of how seriously the White House viewed the potential fallout, Mr Bush appeared on television to read a hastily prepared statement in which he did not deny the allegations, but insisted that his Administration had not broken any laws.

A report in the newspaper USA Today, which claimed that since the 9/11 attacks the National Security Agency (NSA) has secretly collected the records of billions of domestic calls, also cast doubt on the confirmation prospects for General Michael Hayden, Mr Bush’s choice to head the CIA.

General Hayden was head of the NSA between 1999 and 2005 and would have overseen the call-tracking programme. Meetings that General Hayden had scheduled for yesterday with the Republican senators Rick Santorum and Lisa Murkowski before his confirmation hearings on Tuesday were abrubtly cancelled.

According to the newspaper report, the NSA used data secretly handed over by the country’s three largest phone companies — AT&T, Verizon and BellSouth — to try to build a database of every call made within the US — the largest database assembled anywhere in the world, one source said.

The programme does not involve the NSA listening to or recording conversations but the spy agency is using the millions of phone numbers handed over — personal, business and mobile phone records — to look for any “calling patterns” to help to detect terrorist activity.

The programme is significantly different from — and potentially far more damaging politically than the secret, warrantless wiretapping programme revealed in December. That involved monitoring calls and e-mails in which one party was abroad. Polls consistently showed that a significant majority of Americans backed Mr Bush on that because they believed it specifically targeted terror suspects.

Frank Luntz, a Republican pollster, told The Times: “There is a very fine line between national security and personal oppression. The public is prepared to accept a degree of intelligence intervention but this may have crossed the line. I think a majority of Americans will be opposed to this.”

A Senate Judiciary Committee hearing that had been due to discuss judicial nominations was dominated by the revelations. Arlen Specter, its Republican chairman, said he would call the heads of the three telecommunications companies before the panel “to figure out what is going on”.

Patrick Leahy, the senior Democrat on the committee, said: “Are you telling me that tens of millions of Americans are involved with al-Qaeda? These are . . . Americans who are not suspected of anything — where does it stop?” General Hayden said last night: “Everything the NSA does is lawful and carefully done, and the appropriate members of congress are briefed on all NSA activities.”

Mr Bush, facing yet another controversy before November’s congressional elections, said: “We are not mining or trolling through the personal lives of innocent Americans.”

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