A Democratic senator has pressed ahead with this threat to release emails that purportedly link Donald Trump's nominee for the Supreme Court to racial profiling, after saying he was prepared to knowingly break the rules of the US senate.

“I am right now, before your process is finished, going to release the email about racial profiling, and I understand the penalty comes with potential ousting from the Senate,” said Cory Booker, as senators quizzed judge Brett Kavanaugh for a second day.

Later, Mr Booker released approximately 12 pages of emails tied to discussions Mr Kavanaugh had on racial inequality while working for the George Bush White House.

In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing Show all 21 1 /21 In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing WASHINGTON, DC - SEPTEMBER 04: Protesters disrupt the confirmation hearing for Supreme Court nominee Judge Brett Kavanaugh before the Senate Judiciary Committee in the Hart Senate Office Building on Capitol Hill September 4, 2018 in Washington, DC. Kavanaugh was nominated by President Donald Trump to fill the vacancy on the court left by retiring Associate Justice Anthony Kennedy. (Photo by Chip Somodevilla/Getty Images) Chip Somodevilla Getty Images In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing A member of Code Pink protests as US Supreme Court nominee Brett Kavanaugh arrives on the first day of his confirmation hearing in front of the US Senate on Capitol Hill in Washington DC, on September 4, 2018. - President Donald Trump's newest Supreme Court nominee Brett Kavanaugh is expected to face punishing questioning from Democrats this week over his endorsement of presidential immunity and his opposition to abortion. Some two dozen witnesses are lined up to argue for and against confirming Kavanaugh, who could swing the nine-member high court decidedly in conservatives' favor for years to come. Democrats have mobilized heavily to prevent his approval. (Photo by Brendan Smialowski / AFP)BRENDAN SMIALOWSKI/AFP/Getty Images BRENDAN SMIALOWSKI AFP/Getty Images In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing epa06996310 Circuit judge Brett Kavanaugh prepares to testify before his Senate confirmation hearing to be an Associate Justice of the Supreme Court of the United States in the Hart Senate Office Building in Washington, DC, USA, 04 September 2018. President Trump nominated Kavanaugh to fill the seat of retiring justice Anthony Kennedy. If confirmed, Kavanaugh would give conservatives a five-member majority in the high court. EPA/MICHAEL REYNOLDS MICHAEL REYNOLDS EPA In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing WASHINGTON, DC - SEPTEMBER 04: Protesters dressed in The Handmaid's Tale costume, protest outside the hearing room where Supreme Court nominee Judge Brett Kavanaugh will testify before the Senate Judiciary Committee during his Supreme Court confirmation hearing in the Hart Senate Office Building on Capitol Hill September 4, 2018 in Washington, DC. Kavanaugh was nominated by President Donald Trump to fill the vacancy on the court left by retiring Associate Justice Anthony Kennedy. (Photo by Win McNamee/Getty Images) Win McNamee Getty Images In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing A protester is removed during a hearing of the Senate Judiciary Committee on the nomination of Brett Kavanaugh to the US Supreme Court September 4, 2018 in Washington, DC. - President Donald Trump's newest Supreme Court nominee Brett Kavanaugh is expected to face punishing questioning from Democrats this week over his endorsement of presidential immunity and his opposition to abortion. Some two dozen witnesses are lined up to argue for and against confirming Kavanaugh, who could swing the nine-member high court decidedly in conservatives' favor for years to come. Democrats have mobilized heavily to prevent his approval. (Photo by Brendan Smialowski / AFP)BRENDAN SMIALOWSKI/AFP/Getty Images BRENDAN SMIALOWSKI AFP/Getty Images In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing A woman stands and voices her opposition to Supreme Court nominee Brett Kavanaugh, during a Senate Judiciary Committee confirmation hearing on his nomination for Supreme Court, on Capitol Hill, Tuesday, Sept. 4, 2018, in Washington. (AP Photo/Jacquelyn Martin) Jacquelyn Martin AP In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing WASHINGTON, DC - SEPTEMBER 04: Supreme Court nominee Judge Brett Kavanaugh arrives for testimony before the Senate Judiciary Committee during his Supreme Court confirmation hearing in the Hart Senate Office Building on Capitol Hill September 4, 2018 in Washington, DC. Kavanaugh was nominated by President Donald Trump to fill the vacancy on the court left by retiring Associate Justice Anthony Kennedy. (Photo by Win McNamee/Getty Images) Win McNamee Getty Images In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing WASHINGTON, DC - SEPTEMBER 04: Protesters disrupt the start of the Supreme Court nominee Judge Brett Kavanaugh's confirmation hearing before the Senate Judiciary Committee in the Hart Senate Office Building on Capitol Hill September 4, 2018 in Washington, DC. Kavanaugh was nominated by President Donald Trump to fill the vacancy on the court left by retiring Associate Justice Anthony Kennedy. (Photo by Mark Wilson/Getty Images) Mark Wilson Getty Images In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing A protestor is carried out by security as US Supreme Court nominee Brett Kavanaugh attends the first day of his confirmation hearing in front of the US Senate on Capitol Hill in Washington DC, on September 4, 2018. - President Donald Trump's newest Supreme Court nominee Brett Kavanaugh is expected to face punishing questioning from Democrats this week over his endorsement of presidential immunity and his opposition to abortion. Some two dozen witnesses are lined up to argue for and against confirming Kavanaugh, who could swing the nine-member high court decidedly in conservatives' favor for years to come. Democrats have mobilized heavily to prevent his approval. (Photo by Brendan Smialowski / AFP)BRENDAN SMIALOWSKI/AFP/Getty Images BRENDAN SMIALOWSKI AFP/Getty Images In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing A woman stands and voices her opposition to Supreme Court nominee Brett Kavanaugh, during a Senate Judiciary Committee confirmation hearing on his nomination for Supreme Court, on Capitol Hill, Tuesday, Sept. 4, 2018, in Washington.(AP Photo/Jacquelyn Martin) Jacquelyn Martin AP In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing A protestor is escorted out of the room as US Supreme Court nominee Brett Kavanaugh attends the first day of his confirmation hearing in front of the US Senate on Capitol Hill in Washington DC, on September 4, 2018. - President Donald Trump's newest Supreme Court nominee Brett Kavanaugh is expected to face punishing questioning from Democrats this week over his endorsement of presidential immunity and his opposition to abortion. Some two dozen witnesses are lined up to argue for and against confirming Kavanaugh, who could swing the nine-member high court decidedly in conservatives' favor for years to come. Democrats have mobilized heavily to prevent his approval. (Photo by Brendan Smialowski / AFP)BRENDAN SMIALOWSKI/AFP/Getty Images BRENDAN SMIALOWSKI AFP/Getty Images In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing U.S. Supreme Court nominee judge Brett Kavanaugh points to his daughters as his wife Ashley looks on before the start of his Senate Judiciary Committee confirmation hearing on Capitol Hill in Washington, U.S., September 4, 2018. REUTERS/Chris Wattie CHRIS WATTIE REUTERS In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing A woman protests as US Supreme Court nominee Brett Kavanaugh arrives on the first day of his confirmation hearing in front of the US Senate on Capitol Hill in Washington DC, on September 4, 2018. - President Donald Trump's newest Supreme Court nominee Brett Kavanaugh is expected to face punishing questioning from Democrats this week over his endorsement of presidential immunity and his opposition to abortion. Some two dozen witnesses are lined up to argue for and against confirming Kavanaugh, who could swing the nine-member high court decidedly in conservatives' favor for years to come. Democrats have mobilized heavily to prevent his approval. (Photo by Brendan Smialowski / AFP)BRENDAN SMIALOWSKI/AFP/Getty Images BRENDAN SMIALOWSKI AFP/Getty Images In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing U.S. Capitol police officer lead detained protesters out of the start of U.S. Supreme Court nominee Judge Brett Kavanaugh's Senate Judiciary Committee confirmation hearing on Capitol Hill in Washington, U.S., September 4, 2018. REUTERS/Joshua Roberts JOSHUA ROBERTS REUTERS In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing A protester is removed during a hearing of the Senate Judiciary Committee on the nomination of Brett Kavanaugh to the US Supreme Court September 4, 2018 in Washington, DC. - President Donald Trump's newest Supreme Court nominee Brett Kavanaugh is expected to face punishing questioning from Democrats this week over his endorsement of presidential immunity and his opposition to abortion. Some two dozen witnesses are lined up to argue for and against confirming Kavanaugh, who could swing the nine-member high court decidedly in conservatives' favor for years to come. Democrats have mobilized heavily to prevent his approval. (Photo by Brendan Smialowski / AFP)BRENDAN SMIALOWSKI/AFP/Getty Images BRENDAN SMIALOWSKI AFP/Getty Images In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing A protester is removed during a Senate Judiciary Committee confirmation hearing for U.S. Supreme Court nominee judge Brett Kavanaugh on Capitol Hill in Washington, U.S., September 4, 2018. REUTERS/Joshua Roberts JOSHUA ROBERTS REUTERS In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing A protester is removed during a hearing of the Senate Judiciary Committee on the nomination of Brett Kavanaugh to the US Supreme Court September 4, 2018 in Washington, DC. - President Donald Trump's newest Supreme Court nominee Brett Kavanaugh is expected to face punishing questioning from Democrats this week over his endorsement of presidential immunity and his opposition to abortion. Some two dozen witnesses are lined up to argue for and against confirming Kavanaugh, who could swing the nine-member high court decidedly in conservatives' favor for years to come. Democrats have mobilized heavily to prevent his approval. (Photo by Brendan Smialowski / AFP)BRENDAN SMIALOWSKI/AFP/Getty Images BRENDAN SMIALOWSKI AFP/Getty Images In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing epa06996576 A protester is removed as circuit judge Brett Kavanaugh appears before his Senate confirmation hearing to be an Associate Justice of the Supreme Court of the United States in the Hart Senate Office Building in Washington, DC, USA, 04 September 2018. President Trump nominated Kavanaugh to fill the seat of retiring justice Anthony Kennedy. If confirmed, Kavanaugh would give conservatives a five-member majority in the high court. EPA/JIM LO SCALZO JIM LO SCALZO EPA In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing epa06996814 Protesters inside the Hart Senate Office building under arrest as Brett Kavanaugh appears before his Senate confirmation hearing to be an Associate Justice of the Supreme Court of the United States in the Hart Senate Office Building in Washington, DC, USA, 04 September 2018. President Trump nominated Kavanaugh to fill the seat of retiring justice Anthony Kennedy. If confirmed, Kavanaugh would give conservatives a five-member majority in the high court. EPA/TASOS KATOPODIS TASOS KATOPODIS EPA In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing US Capitol Police arrest a protestor during the US Senate Judiciary Committee confirmation hearing for Judge Brett Kavanaugh to be an Associate Justice on the US Supreme Court, on Capitol Hill in Washington, DC, September 4, 2018. - President Donald Trump's newest Supreme Court nominee Brett Kavanaugh is expected to face punishing questioning from Democrats this week over his endorsement of presidential immunity and his opposition to abortion. Some two dozen witnesses are lined up to argue for and against confirming Kavanaugh, who could swing the nine-member high court decidedly in conservatives' favor for years to come. Democrats have mobilized heavily to prevent his approval. (Photo by SAUL LOEB / AFP)SAUL LOEB/AFP/Getty Images SAUL LOEB AFP/Getty Images In pictures: Chaos and fury at Brett Kavanaugh's confirmation hearing US Capitol Police arrest a protestor during the US Senate Judiciary Committee confirmation hearing for Judge Brett Kavanaugh to be an Associate Justice on the US Supreme Court, on Capitol Hill in Washington, DC, September 4, 2018. - President Donald Trump's newest Supreme Court nominee Brett Kavanaugh is expected to face punishing questioning from Democrats this week over his endorsement of presidential immunity and his opposition to abortion. (Photo by SAUL LOEB / AFP)SAUL LOEB/AFP/Getty Images SAUL LOEB AFP/Getty Images

ABC News said the move by Mr Booker came as Democrats complained that documents were still being withheld. Senate Judiciary Committee chairman Chuck Grassley, a Republican, said Democrats who had protested that some documents were not available had an opportunity to make their complaints beforehand but waited to do it publicly to delay the hearing.

The documents in question were not classified, it said, but are marked “committee confidential”, meaning members of the committee have access to them but they were not released to the public. Mr Grassley hasd reportedly designated as many as 141,000 pages of documents from Kavanaugh’s record as “committee confidential”.

Mr Booker’s threat to break senate rules resulted in Republican John Cornyn of Texas, accusing Mr Booker of “conduct unbecoming of a senator”.

“Running for president is no excuse for violating the rules of the senate or of confidentiality of the documents that we are privy to,” Mr Cornyn said of Mr Booker, who is considered a possible Democratic contender for president in 2020.

Mr Booker said one email from Mr Kavanaugh, written while he was working with Mr Bush and which had not been made available to the public, showed the nominee was sympathetic to racial profiling by police.

Supreme court nominee Brett Kavanaugh snubs handshake from father of slain Parkland student

The document in dispute was a 2002 email with the subject line “racial profiling” that included internal White House discussions about whether airport security and other law enforcement should strive for a “race-neutral” system in the wake of the September 11 terror attacks.

In one of the emails, Mr Kavanaugh referred to a possible interim policy and wrote: “The people (such as you and I) who generally favour effective security measures that are race-neutral DO need to grapple - and grapple now — with the interim question of what to do before a truly effective and comprehensive race-neutral system is implemented.” On Wednesday, Mr Booker had questioned Mr Kavanaugh about his use of the term “naked racial set-aside”, and said he would make public documents backing up that assertion.

Shortly after Mr Booker acted, Mr Grassley's staff released a bulk of new emails, previously marked “committee confidential”. that had been cleared for public release.

Some speculated whether Mr Booker's may have been playing for the cameras. The Hill said a spokesman for the Senate Judiciary Committee, said Mr Booker was not breaking any confidentiality rules.

“Restrictions were waived before 4.00am this morning and made ready for release,” he said.

On Wednesday, three progressive groups – Demand Justice, MoveOn and NARAL Pro-Choice America – urged Democrats to go around Mr Grassley and release more records related to Mr Kavanaugh’ record as a judge. For the last 12 years he has served as appeals court judge in Washington DC, considered the second most important court other than the Supreme Court.

“Chairman Grassley must not shield Judge Kavanaugh from evidence that Kavanaugh perjured himself in previous confirmation hearings, or any other documents or evidence relevant to his ability to serve on the highest court for a lifetime appointment,” said the statement. “Democrats know that nothing in the Senate Standing Rules or Judiciary Committee Rules grants Grassley sole authority to designate documents ‘committee confidential’ or prohibit their public release.”

Meanwhile, Mr Kavanaugh, raised questions as a White House aide more than a decade ago about whether the 1973 high court ruling legalising abortion was settled in law, the New York Times reported on Thursday, citing more leaked emails.

The Times said an “unknown person” provided several confidential emails to the newspaper late on Wednesday relating to Mr Kavanaugh’s work in the White House under Mr Bush. A lawyer for Bush previously turned over thousands of documents to the Senate Judiciary Committee that the Republican-led panel deemed “committee confidential”.