A Democratic senator has released 28 further confidential documents related to the nomination of Brett Kavanaugh, Donald Trump‘s nominee for the US Supreme Court, despite threats of an ethics investigation.

The documents released by Cory Booker are from Mr Kavanaugh’s time working in the White House for the administration of George W Bush.

They are marked “committee confidential” meaning although they were not classified, they were only to be seen by the Senate Judiciary Committee and not to be released to the public.

The new emails do not directly contradict the testimony Mr Kavanaugh provided to the US Senate earlier this month.

But Mr Booker claims the documents show Mr Kavanaugh misled the Senate Judiciary Committee over a decade ago, during confirmation hearings for his current position on the US Court of Appeals for the District of Columbia Circuit.

Mr Kavanaugh told the committee in 2006 he was not closely involved with Mr Bush’s nomination of Charles Pickering to the US Court of Appeals for the Fifth Circuit.

Mr Pickering was a controversial choice due to his record on civil rights.

The newly released emails show Mr Kavanaugh was in fact involved in the nomination process, according to The Hill.

“These documents suggest Judge Kavanaugh misled the Senate Judiciary Committee during his prior testimony,” said Mr Booker.

“This is a grave and worrisome prospect given the fact that Judge Kavanaugh is up for a lifetime appointment to our nation’s highest court with the potential to change American law for decades to come.”

Mr Booker wrote on Twitter that he would continue releasing documents as it was “important that American people see Kavanaugh’s entire record.”

Mr Booker previously released 12 documents purporting to tie Mr Kavanaugh to racial profiling, after declaring that he was prepared to break Senate rules.