Republicans and Democrats on the House Oversight and Government Reform Committee disagree on whether to ask the president to remove the head of the IRS, with Republicans slamming the commissioner's relatively short track record and Democrats criticizing the majority's "manufactured crisis" of an ongoing IRS scandal.

Led by Chairman Jason Chaffetz, 21 lawmakers on the committee urged President Obama to remove IRS Commissioner John Koskinen amid evidence that the tax agency official had obstructed the committee's investigation of IRS targeting,

But Rep. Elijah Cummings, the committee's top Democrat, dismissed the majority's move.

"This is a strange, oddly-timed rehashing of conspiracy theories that were debunked by the Inspector General himself — who concluded in a report to the Oversight Committee just last month that there is no evidence to substantiate these claims," the Maryland Democrat said.

"Calls for Commissioner Koskinen to step down are nothing more than a manufactured Republican political crisis based on allegations that have already been debunked," Cummings added.

Koskinen took charge of the IRS in late 2013 amid controversy over the tax agency's systematic targeting of Tea Party groups applying for nonprofit status.

He was soon forced to answer for thousands of undisclosed emails sent to and from Lois Lerner, the former head of the IRS tax exempt unit.

With many of those records still unaccounted for, Republican lawmakers are now calling for a change of leadership at the IRS.

The oversight committee sent its first subpoena for Lerner's emails to the IRS in August of 2013, roughly three months after the tax agency's inspector general revealed evidence of that conservative applicants were singled out for extra scrutiny.

The committee reissued that subpoena in February of last year in the wake of Koskinen's confirmation to his present position.

"Under his leadership, the IRS failed to look in five of the six places where Ms. Lerner's emails could potentially be recovered," committee members wrote in a letter to the president.

According to the letter, the IRS didn't examine Lerner's Blackberry phones, her email server, her back-up email server, a laptop she was loaned or the agency's back-up tapes.

However, Koskinen testified in March of last year that his agency would produce all of Lerner's emails.

"According to testimony later received by the committee, the IRS knew at the time Commissioner Koskinen's appearance in March 2014 that Lerner's emails had been destroyed," the Republicans wrote in their letter to the president.

Lerner's crashed hard drive had apparently been recycled the same month she requested a copy of paperwork filed by Crossroads GPS, an influential conservative group.

Aaron Signor, the IRS technician who first inspected Lerner's hard drive in 2011 to determine whether it had crashed, told congressional investigators that her laptop contained large amounts of data.

Signor testified that, after he advised Lerner's assistant that the hard drive needed to be backed up given the volume of data, he was told Lerner was too busy to move her data over and that doing so wasn't her "responsibility."

Lerner's emails weren't the only records that disappeared during critical points in the tax agency's alleged partisan targeting of conservative groups.

The IRS was unable to locate the emails of four other IRS officials. For example, Judy Kindell, Lerner's expert on political speech, lost her emails in August 2010 after the IRS began receiving "media inquiries related to...political speech by conservative nonprofit groups."

In a June 2011 email to a colleague whose hard drive also failed, Lerner noted that "no one will ever believe that both your hard drive and mine crashed within a week of each other!"

Like the House Select Committee on Benghazi's probe of the 2012 terror attack, the congressional investigation of the IRS scandal has been slowed significantly by an agency's reluctance to hand over documents.

Both investigations have become fodder for some Democrats, who accuse Republicans of dragging out investigations that cast an unflattering light on the Obama administration.