WASHINGTON — The head of the IRS wants to be able to call witnesses, present evidence and enjoy other traditional protections if the House formally pursues an effort by conservatives to impeach him, John Koskinen’s lawyers told Congress Friday.

Koskinen has agreed to testify under oath next Wednesday to the Republican-run House Judiciary Committee. The panel plans to quiz the commissioner about conservatives’ claims that he should be impeached for thwarting congressional investigations into his agency’s tough scrutiny of tea party groups seeking tax exemptions.

Koskinen, who didn’t join the IRS until after it had already apologized for its treatment of the conservative groups, has denied the charges.

In a letter Friday, Koskinen’s lawyers told the committee that if it later begins a formal impeachment inquiry, he should be allowed standard procedural protections. They asked that he be allowed to cross-examine witnesses, object to evidence and examine transcripts of interviews conducted by the House Oversight and Government Reform Committee.

The attorneys wrote that otherwise, the process “would be more akin to a foreign show trial than the solemn process contemplated by the framers and generations of congressional leaders.”

Asked if the Judiciary Committee would grant Koskinen’s request, a GOP committee aide said no further decisions have been made.

The Judiciary panel and leaders of the conservative House Freedom Caucus agreed this week to hold the hearing, preventing a full House vote that was set for Thursday on whether to impeach Koskinen.

Conservatives conceded they were likely to have lost that vote, a showdown that GOP leaders preferred to avoid during the run-up to November’s elections.