The commissioner of the IRS declined on Monday to appear at a congressional hearing this week examining whether he deserves to be impeached, but said in a written statement that allegations against him "are without merit."

IRS chief John Koskinen has not had time to prepare for Tuesday's House Judiciary Committee hearing because of travel and because he is also getting ready for an unrelated hearing, the agency said in a statement.

Instead, Koskinen submitted a seven-page statement to the Judiciary panel defending himself.

Some conservative Republicans have been pushing for Koskinen's removal because they say he has prevented congressional investigators from gathering evidence about how the IRS treated conservative groups seeking tax-exempt status. A leader of that effort, Rep. Jason Chaffetz, R-Utah, will testify Tuesday to the Judiciary Committee.

The IRS says it has cooperated over numerous hearings and has submitted over a million pages of documents.

The Justice Department has found no evidence of criminal behavior by the IRS. And the IRS inspector general concluded that while data containing requested agency emails has been destroyed, there is no proof that that was done purposely.

The GOP election-year impeachment effort seems highly unlikely to succeed. It has not won forceful backing from House Speaker Paul Ryan, R-Wis., has drawn lukewarm support from other Republicans and is opposed by Democrats.