John Koskinen
© AP Photo/Jacquelyn Martin, FileIRS Commissioner John Koskinen
House Oversight Committee Chairman Jason Chaffetz began the impeachment process against IRS Commissioner John Koskinen Tuesday, accusing him of misleading the public and destroying documents that were being sought under a congressional subpoena.

It's the latest move in the battle over tea party targeting at the tax agency, and comes less than a week after the Justice Department issued a report finding no criminal behavior in the IRS's decision to subject conservative groups to intrusive scrutiny.

Among the specific charges Mr. Chaffetz and 18 of his fellow Republicans on the committee allege are that Mr. Koskinen misled Congress when he said he'd turned over all of former IRS senior executive Lois G. Lerner's emails, and oversaw destruction of evidence when his agency destroyed backup tapes that contained the emails.

It was unclear how far the resolution would go, in a Congress already preoccupied with so many other fights and with little more than a year to go in President Obama's tenure.

The impeachment resolution says the IRS knew Ms. Lerner's messages were missing, due to a reported computer hard drive crash, as early as February 2014, but didn't notify Congress until June — while the backup tapes were destroyed in March.

Rep. Elijah E. Cummings, the ranking Democrat on the Oversight Committee, said the accusations against Mr. Koskinen were baseless.

"This ridiculous resolution will demonstrate nothing but the Republican obsession with diving into investigative rabbit holes that waste tens of millions of taxpayer dollars while having absolutely no positive impact on a single American," the Maryland Democrat said. "Calling this resolution a 'stunt' or a 'joke' would be insulting to stunts and jokes."

The IRS didn't have an immediate comment Tuesday afternoon on the impeachment resolution.

But just hours earlier, Mr. Koskinen testified to the Senate that he's taken steps to try to clean up the mess left by the targeting scandal.

"The chain of command all the way down has changed. There are new people that have gone through, and we've pursued appropriate disciplinary review as needed," Mr. Koskinen said.

He also acknowledged his agency is still holding up a "handful" of tea party groups' applications — including one that's been waiting for nearly six years, The Washington Times reported earlier this week.

And he said he hopes to have new rules to limit political activities of nonprofit organizations in place before the 2016 election, raising the specter of another major fight over the tax agency and political targeting.

Mr. Koskinen took over at the IRS after the May 2013 revelation that agency employees singled tea party and conservative groups out for special scrutiny, asking intrusive questions and delaying their applications for nonprofit status well beyond reasonable times.

The Obama administration said part of the problem was that the rules were too confusing, leaving the nonprofit groups and IRS auditors uncertain about what activity was allowed.

The IRS has already tried one rewrite of those rules that would have prohibited nonprofit groups from conducting voter registration drives or hosting candidate forums. Overwhelming public opposition forced Mr. Koskinen to nix that proposal, but he said Tuesday he is going to try again.

"We would hope that we'd be able to provide these proposed new rules early enough next year so that they could — the work on them can be completed well in advance of the election so there wouldn't be any confusion," he said. "But I would stress that the work that we're doing now is focused on clarifying — not changing — but clarifying the rules under which organizations operate."

Finance Committee Chairman Orrin G. Hatch told Mr. Koskinen that seemed like a waste of time and money when the IRS is already struggling to handle taxpayers' phone calls during filing season, and losing billions of dollars a year to tax fraud.

Mr. Hatch, Utah Republican, said he'll push to impose more restrictions on IRS employees engaging in political activities outside of work. And he said he'll try to dent the influence agency employees' labor union has, which the senator suspected helped feed the tea party targeting.

"Our overall goal here should be to restore the credibility of the IRS and ensure that this very powerful agency treats all American taxpayers fairly," Mr. Hatch said.

He and other senators were critical of the IRS's decision to award bonuses to some of the officials involved in "bad decisions" that led to the targeting.

"The targeting scandal, coupled with poor customer service and general mismanagement has shaken what confidence taxpayers had in the IRS," said Sen. Charles E. Grassley, Iowa Republican. "To move beyond this, Congress and the IRS are going to have to work together to make the necessary changes to ensure similar abuses can never happen again."