President Bush last night nominated John G Roberts, a conservative judge who once wrote a legal opinion arguing against abortion rights, to fill the first vacancy on the US Supreme Court for a decade, setting up a potentially explosive confirmation battle.

Mr Roberts, 50, a graduate of Harvard Law School, was only promoted to the level of a federal appeals judge by Mr Bush two years ago, but liberal groups have already pledged to fight his nomination with a multi-million dollar advertising campaign.

Within minutes of his nomination being confirmed last night, about 45 minutes before Mr Bush officially announced it in a prime time televised address, Naral, the pro-choice pressure group, said that Mr Roberts was an "unsuitable choice".

But White House aides believe that in choosing Mr Roberts, who as a private lawyer was a key legal adviser for Mr Bush during the 2000 election’s Florida recount drama, they have chosen a rock-solid conservative who will delight the President’s electoral base, but whom Democrats will struggle to block in his Senate confirmation.

Although a brilliant lawyer, who argued more than 39 cases before the Supreme Court, winning 25, Mr Roberts has sat on the US Court of Appeals for the DC Circuit only since 2003. His short tenure on the bench means fewer written opinions and a sparse paper trail available for Democrats to attack.

Nevertheless, liberals say that Mr Roberts has taken positions in cases involving free speech and religious liberty that endanger those rights. They allege that Mr Roberts is hostile to abortion rights and cite a brief he co-wrote in 1990 that suggested the Supreme Court overturn Roe v Wade, the landmark 1973 high court decision that gave women a constitutional right to abortion.

The brief, written for the first President Bush’s administration in a 1991 abortion case, stated that "we continue to believe that Roe v Wade was wrongly decided and should be overruled. The court’s conclusion in Roe that there is a fundamental right to an abortion ... finds no support in the text, structure or history of the Constitution".

Such language will delight conservatives. After the resignation last month of Sandra Day O’Connor, the first female Supreme Court justice, Mr Bush has been under intense pressure from his base to pick an established social conservative, with clear anti-abortion credentials, to help tip the ideology of the finely-balanced nine-member court decisively their way.

However, Mr Roberts also told senators during his 2003 confirmation hearing to the DC appeals court that he would be guided by legal precedent.

"Roe v Wade is the settled law of the land," he said at the time. "There is nothing in my personal views that would prevent me from fully and faithfully applying that precedent."

Because the Supreme Court adjudicates over issues including abortion, gay marriage, affirmative action and the separation of Church and state, there has been no issue more important to Mr Bush’s base than how he would use this rare chance to reshape the court to suit his own conservative philosophy. Supreme Court justices are lifetime appointments.

With William Rehnquist, the chief justice, suffering from thyroid cancer, Mr Bush will likely have another vacancy to fill before he leaves the White House, and conservatives have been preparing for this moment for years.

The danger for Mr Bush is that a protracted confirmation battle could doom much of his second-term agenda. But analysts believe that Mr Roberts, a Washington insider who has worked over the years at the White House, Justice Department and in private practice, is such a highly qualified candidate, and such a brilliant jurist, that Democrats will find it hard to block his appointment.

In the Reagan administration, Mr Roberts was special assistant to the Attorney-General and associate counsel to the President. Between 1989 and 1993, he was principal deputy solicitor general, the government’s second highest lawyer who argues cases before the US Supreme Court.

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