Lawyers for former President Donald J. Trump are seeking more information about discussions Atlanta prosecutors had with the Biden White House, as well as with the House committee that investigated the Jan. 6, 2021, attack on the U.S. Capitol.

Mr. Trump has claimed for some time that the election interference case brought against him by Fani T. Willis, the district attorney in Fulton County, Ga., is tainted by ties to both entities. A legal filing this week from one of Mr. Trump’s co-defendants in the case provided new details about the contacts. The former president and 14 of his allies face racketeering and other charges in the inquiry.

It has been known since 2021, when Ms. Willis’s began her investigation, that she sought to make use of evidence gathered by the House Jan. 6 committee. Her office’s contacts with the White House Counsel’s Office came in 2022, as she was gathering facts and evidence about the conduct of Trump White House officials and seeking to compel their testimony before a special grand jury.

One of the officials who would be subpoenaed to testify was a former White House counsel, Pat Cipollone.

The disclosures came in expense reports from Nathan Wade, the outside lawyer hired by Ms. Willis to lead the Trump prosecution. They were included in a public filing this week from Michael Roman, a former Trump campaign official who is a defendant in the case.

The filing thrust Mr. Wade into the spotlight, accusing him of being romantically involved with Ms. Willis and suggesting that their relationship was the reason she chose Mr. Wade for the high-paying job. Lawyers for Mr. Wade’s wife, Jocelyn Wade, issued a subpoena this week to Ms. Willis, seeking her appearance in a divorce action that is in progress.