Washington (CNN) House Democrats asked a federal appeals court on Thursday to swiftly order former White House Counsel Don McGahn to testify in the House, saying arguments made by President Donald Trump's legal team during the impeachment trial have undercut the Justice Department's position in the long-simmering legal battle over McGahn's testimony.

The House Judiciary Committee subpoenaed McGahn in the wake of the Mueller report, before Trump's infamous call with Ukrainian President Volodymyr Zelensky. Recently, House lawyers said they'd use McGahn's testimony to boost their impeachment case.

The Justice Department has previously argued in court that the House doesn't have any legal grounds to bring lawsuits to enforce subpoenas. But Trump's lawyers argued this week in the impeachment trial that the House should have fought harder in the courts to enforce their subpoenas and the Senate shouldn't condone their negligence by bringing in new witnesses.

The lawsuit revolves around McGahn's potential testimony to the House Judiciary Committee. Separately, congressional Democrats are pushing for the Senate to issue subpoenas for testimony from new witness for Trump's impeachment trial.

"President Trump's arguments in the impeachment trial contradict DOJ's assertion in this case that the (House Judiciary) Committee may not seek to enforce its subpoenas in court," the House's top lawyer, Doug Letter, wrote in a letter to the DC Circuit Court of Appeals.

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