After the indictment on Friday of Lewis “Scooter” Libby, Vice-President Cheney’s chief of staff, for his role in blowing the cover of a CIA official, Mr Bush was also under mounting pressure to launch an investigation of Mr Cheney’s office along with a staff shake-up.

After one of the worst weeks of Mr Bush’s presidency, new polls revealed how seriously Mr Libby’s indictment for perjury and obstruction of justice has undermined public confidence in the White House.

Already struggling to deal with an increasingly unpopular war in Iraq, the withdrawal last week of his Supreme Court nominee Harriet Miers in the face of a Republican mutiny, and the Hurricane Katrina disaster, Mr Bush’s approval rating has slumped to just 39 per cent, according to a Washington Post/ABC News poll. A majority of Americans — 55 per cent — said that the charges signalled broader ethical problems in the Administration. By a ratio of three to one, those surveyed said the level of honesty in government had declined during Mr Bush’s tenure.

Although Patrick Fitzgerald, the prosecutor in charge of the leak investigation, has no plans to charge Mr Cheney, the affair has cast a harsh spotlight on a Vice-President used to working in the shadows.

Mr Libby’s indictment raises the prospect of a trial that will focus in part on the role Mr Cheney played in building the case for the invasion of Iraq by using intelligence subsequently found to be flawed.

Lindsey Graham, a Republican senator from South Carolina, said that Mr Bush should investigate Mr Cheney’s office. Harry Reid, the Democrat leader in the Senate, said Mr Bush and Mr Cheney should apologise for the actions of Mr Libby and Mr Rove. He said that the President and Vice-President “should come clean with the American people”.

Christopher Dodd and Charles Schumer, Democrat senators, called for an investigation of Mr Cheney’s office.

Although Mr Fitzgerald implied on Friday that an indictment of Mr Rove was unlikely, the legal uncertainty hanging over Mr Bush’s closest aide looked set to cause the White House more problems.

Despite avoiding charges last week, Mr Rove was revealed by the investigation to have been one of the White House officials involved in the leaking of the name of Valerie Plame, the CIA official, to the media.

Trent Lott, the former Republican Senate Leader, implied yesterday that the continued cloud hanging over Mr Rove might make him expendable.

“If he (Rove) has a problem, I think he’s got to step up and . . . acknowledge that and deal with it,” Mr Lott said. Mr Libby’s lawyer, Joseph Tate, outlined his defence strategy, saying that his client had not deliberately lied about his conversations with journalists about Ms Plame, but had such a hectic job that his memory was not clear about the events in question. Meanwhile, Mr Bush will try this week to relaunch his beleaguered presidency, starting with the nomination of a reliable conservative to the Supreme Court. That will help to reunify a fractured Republican party and shore up support among his conservative base but it also opens the prospect of a potentially damaging Senate showdown with Democrats.

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