JUDGE Brett Kavanaugh has been confirmed to the US Supreme Court today despite the sexual assault allegations levelled against him.

By a vote of 50-48, the Senate gave a lifetime job to the conservative nominee, 53, after weeks of fierce debate over sexual violence that has divided the US.

Kavanaugh was sworn in by Chief Justice John Roberts and the retiring Justice Anthony Kennedy, who he is replacing.

The vote is a bitter blow to Democrats already seething at Republican control of the White House and both chambers of the US Congress.

Kavanaugh's nomination was overshadowed by university professor Christine Blasey Ford who accused him of sexually assaulting her at a high school party in a wealthy suburb of Washington in 1982.

Two other women accused him in the media of sexual misconduct in the 1980s.

Kavanaugh denied the accusations in a tearful testimony before the Senate Judiciary Committee that was viewed live on television by around 20million people.

Trump stood by his nominee, a federal appeals court judge with a history of advancing Republican causes.

The US President this week mocked Ford's account of what she says was a drunken attack on her by Kavanaugh when they were teenagers.

Trump said on Saturday before the vote that Kavanaugh would do a "great, great" job there.

Following the vote, the Republican firebrand tweeted: “I applaud and congratulate the US Senate for confirming our GREAT NOMINEE, Judge Brett Kavanaugh, to the United States Supreme Court.

“Later today, I will sign his Commission of Appointment, and he will be officially sworn in. Very exciting!”

Kavanaugh will join four liberal justices and four other conservatives as the court, which is expected soon to hear controversial disputes involving abortion, immigration, gay rights and voting rights.

Republicans hold only a 51-49 Senate majority and therefore had little support to spare.

It was the closest roll call to confirm a justice since 1881, when Stanley Matthews was approved by 24-23, according to Senate records.

The FBI had been tasked by the US President to look into allegations of sexual misconduct levelled against the judge.

But after Republican Senator Susan Collins and Joe Manchin, a Democrat, both indicated their backing his seat looked all but confirmed.

Kavanaugh's confirmation gives conservatives a solid 5-4 majority in future legal battles on contentious issues such as abortion rights, immigration and gay and transgender rights.

About 100 anti-Kavanaugh protesters climbed the Capitol's East Steps as the vote approached, pumping fists and waving signs, leading to some arrests.