US President Donald Trump has apologised to Brett Kavanaugh and his family for their “terrible suffering” during the Supreme Court confirmation process.

At a ceremonial swearing in at the White House on Tuesday, Mr Trump slammed Mr Kavanaugh’s opponents for a “campaign of personal destruction” and apologised “on behalf of the nation”.

The President said that “under historic scrutiny”, Kavanaugh was “proven innocent”.

“Those who stepped forward to serve our country deserve a fair and dignified evaluation. Not a campaign of political and personal destruction based on lies and deception,” he said.

Mr Kavanaugh responded by praising the President and portrayed himself as a non-political jurist.

“The Senate confirmation process was contentious and emotional,” Mr Kavanaugh acknowledged.

“My focus is on being the best justice I can be … A force for stability and unity. My goal is to be a great justice for all Americans and for all of America.”

Earlier in the day Mr Trump had claimed Mr Kavanaugh was “caught up in a hoax that was set up by the Democrats”.

“It was all made up, it was fabricated and it’s a disgrace,” the President  said.

The bitter partisan fight over the nomination became a firestorm after sexual misconduct allegations emerged involving Mr Kavanaugh.

He emphatically denied the allegations and was eventually confirmed in a 50-48 vote – the closest vote to confirm a justice since 1881.

The other eight justices were at Monday’s ceremony. Mr Kavanaugh officially became a member of the high court on Saturday.

Mr Kavanaugh has already been at the Supreme Court preparing for his first day on the bench on Tuesday and has appointed an all-woman staff of clerks.

“A clerkship on the Supreme Court is one of the most coveted achievements and credentials in American law,” Mr Kavanaugh said at the ceremony.

“I’m proud that all four of my newly hired law clerks at the Supreme Court are women, a first in the history of the Supreme Court.”

-with AAP