WASHINGTON — Sen. Cory Booker on Wednesday night released a new batch of confidential documents about Supreme Court nominee Brett Kavanaugh even after a conservative judicial group referred his earlier disclosures to the Senate Ethics Committee.

The 28 new documents from Kavanaugh's time in the White House counsel's office during the George W. Bush administration show his involvement in judicial nominations, including for some of the more controversial judges of the era.

Booker, a New Jersey Democrat, is being criticized by his GOP colleagues and outside groups for releasing the documents, which the Judiciary Committee is holding back on a confidential basis that makes them accessible only to senators. Last week, he released some documents that were later made public by the committee, as well as others that weren't. Wednesday's disclosure brings the total to 75.

Booker said the documents about Kavanaugh's work "raise more serious and concerning questions" about his honesty during his testimony before the committee when he suggested he was not substantially involved in the nominations.

At the same time, the conservative group Judicial Watch delivered a letter Wednesday to the Senate Ethics Committee seeking an investigation. It says Booker violated Senate rules against disclosing confidential documents and could face Senate expulsion.

Booker "explicitly invited his expulsion from the Senate in his egregious violation of the rules and contempt for the rule of law and the Constitution," said Judicial Watch President Tom Fitton.

At issue has been the unprecedented process the Senate Judiciary Committee used for gathering documents on Kavanaugh, an appellate court judge who is President Donald Trump's nominee to replace retired Justice Anthony Kennedy on the court. The Senate is expected to vote on his confirmation by the end of the month.

The committee was hoping to quickly process Kavanaugh's unusually long paper trail and relied on Bush's lawyer, Bill Burck, to compile the documents, first estimated to be 900,000 pages from Kavanaugh's time in the counsel's office. Eventually, some 267,000 pages were made public and 174,000 were held as committee confidential.

Democrats have complained the process was a "sham," as Booker put it. It also excluded any documents Democrats wanted to see from Kavanaugh's time as Bush's staff secretary.

But Burck's team stood by the process, according to a letter to the committee Wednesday obtained by The Associated Press. They remain willing to review documents and consent to senators' requests for disclosure, "when appropriate," the letter said. Despite those commitments, the letter said one member of the committee has released more than 40 documents without consent, referring to Booker.

"Had we been consulted on these universally released documents, we would have consented to their public disclosure," the letter said.

The documents released Wednesday show Kavanaugh's involvement in Bush's nomination of Charles Pickering to an appellate court in the South amid questions about his views on race relations. The Senate blocked the nomination, but Bush later made a recess appointment. Pickering has since retired from the bench.

Kavanaugh submitted a 263-page response late Wednesday to some 1,287 written questions from senators following last week's confirmation hearing. All but nine of the questions were from Democrats.

White House spokesman Raj Shah said, "Despite the endless complaints from critics, the committee has received more material regarding Judge Kavanaugh's nomination than any nominee in history." He said senators have "more than enough information" to consider Kavanaugh's nomination.