At the time, Senators Richard J. Durbin, Democrat of Illinois, and Patrick J. Leahy, Democrat of Vermont, suggested that Judge Kavanaugh may have lied during his confirmation hearing the previous year. A spokesman for the judge insisted at the time that his testimony had been accurate, and the Justice Department’s public integrity section decided not to bring charges.

This summer, after President Trump nominated Judge Kavanaugh to fill the seat left vacant by Justice Kennedy’s retirement, Mr. Durbin and Mr. Leahy renewed their questions about his 2006 testimony. Judge Kavanaugh’s former colleagues have defended him, saying that terrorism detainee policy was not part of his portfolio and that he had been consulted on that particular question only for insight into Justice Kennedy’s thinking.

On Thursday, Mr. Durbin said in a statement that “even the cherry-picked documents we’ve seen so far include evidence that contradicts Judge Kavanaugh’s sworn testimony from 12 years ago. I can only imagine what is in the documents they are refusing to make public.”

But the Trump White House stressed Thursday that Judge Kavanaugh’s denial of involvement in detention policy arose in a different context: He was responding to questions by Mr. Durbin at the hearing about the torture of terrorism detainees in C.I.A. or military custody.

“At no point did Senator Durbin ask the judge about other legal issues pertaining to the war on terrorism, such as detainees’ legal rights,” said Raj Shah, a White House spokesman.

The email does not indicate whether Judge Kavanaugh went on to brief Mr. Ashcroft about the attorney-client issue in late 2001. But two weeks later, Mr. Ashcroft testified that it was appropriate for the government to monitor attorney-client conversations of “16 of the 158,000 federal inmates,” so long as it did not use the information for prosecuting them because they were suspected of terrorism offenses.