The dispute over the Bush administration's secret eavesdropping of US citizens has reignited after it emerged the White House had brokered a deal with Congress that critics say gives it even greater flexibility to monitor phone calls electronically.

It was widely reported that the agreement between the White House and Senate Judiciary Committee represented an about-turn by President George Bush on a key weapon in his so-called "war on terror". This was because the agreement hammered out with the committee's Republican chairman, Senator Arlen Specter, would allow a secret court to assess the constitutionality of the President's covert eavesdropping programme.

But Democrats said the proposed new legislation merely required the White House to behave in a way it was already legally obliged to in exchange for giving it greater flexibility over the eavesdropping. Other campaigners said the proposed legislation would allow the Bush administration to continue surveillance of US citizens without a warrant.

The controversy about the electronic eavesdropping of Americans first broke late last year when The New York Times revealed the administration has been monitoring overseas telephone conversations and internet communications since the aftermath of 11 September. At the time Mr Bush said that he did not require a court order for this and that the revelation of the programme undermined national security.

Mr Specter claimed the new deal with the White House was a breakthrough because it cleared the way for the secret Foreign Intelligence Surveillance Act (Fisa) court to monitor the eavesdropping programme. "We have structured a bill which is agreeable to the White House and I think will be agreeable to this committee," he claimed.

But Democrats said Mr Bush was already obliged under a 1978 act to obtain permission from the court for such eavesdropping. Senator Patrick Leahy said: "[Mr Bush] is saying, 'If you do every single thing I tell you to do I will do what I should have done anyway'. The President has a right to submit the programme to the Fisa court right now if he wanted." Senator Russ Feingold said: "I will continue to oppose any bill that would grant blanket approval for warrantless surveillance of Americans."

The new bill would give the government seven rather than the current three days to obtain a retroactive warrant to permit eavesdropping in an emergency and grant the administration greater flexibility in claiming what constituted an emergency.

Civil liberties campaigners said the agreement gave the administration greater flexibility. They also said that allowing a secret court to assess the constitutionality of the programme would mean many potentially embarrassing details - for instance, if it was revealed the programme had been used to monitor political opponents - would never be made public.

"The proposal would set up a sham judicial review," said Kate Martin, director of the non-profit group Centre for National Security Studies. "[The Supreme Court has ruled] that the President needs congressional authority.

"This bill would have Congress give authority to the President to continue the surveillance of Americans without a warrant."

The latest twist is part of a broader narrative about challenges to Mr Bush's claimed powers as a "war-time"President. The Supreme Court said recently the administration's way of dealing with prisoners at Guantanamo Bay was unconstitutional. This week, the administration said all prisoners in the custody of the Pentagon would be afforded the rights of the Geneva Conventions, something it had previously rejected.