Charles Dharapak / AP

House Oversight and Government Reform Committee Chairman Rep. Darrell Issa, R-Calif., right, talks with the committee's ranking Democrat Rep. Elijah Cummings, D-Md. on Capitol Hill in Washington, Thursday, June 6, 2013, during the committee's hearing regarding IRS conference spending.

A top GOP lawmaker pushed back Sunday against a Democratic colleague’s claim that all questions stemming from the Internal Revenue Service’s targeting of Tea Party groups have been sufficiently answered.

Rep. Darrell Issa, the House Oversight and Government Reform Committee Chairman and frequent White House detractor, slammed comments made by Rep. Elijah Cummings Sunday that the case of allegedly unwarranted investigations of conservative activist groups has been "solved."

"I strongly disagree with Ranking Member Cummings’ assertion that we know everything we need to know about inappropriate targeting of Tea Party groups by the IRS,” Issa (R-Calif.) said in a statement released Sunday after Cummings (D-Maryland) appeared on CNN.

"His extreme and reckless assertions are a signal that his true motivation is stopping needed Congressional oversight and he has no genuine interest in working, on a bipartisan basis, to expose the full truth," Issa's statement read.

Cummings had earlier appeared on CNN’s “State of the Union” and claimed that the "conservative Republican" manager of Cincinnati-based IRS screeners responsible for 501(c)(4) probes told congressional investigators that there was no evidence the Obama administration had a role in the agency’s alleged targeting of Tea Party groups.

The claims run counter to allegations made by many leading Republicans that the IRS took orders from political operatives associated with Obama’s re-election campaign.

"He is a conservative Republican working for the IRS," Cummings said of the unidentified manager. "I think this interview and these statements go a long way to showing that the White House was not involved in this."

What’s more, Cummings said the investigation completed by the House Oversight Committee showed that there was no need to extend a federal probe.

"Based upon everything I've seen, the case is solved,” Cummings said. "If it were me, I would wrap this case up and move on."

Issa disputed Cummings' claims in his statement, saying that the "American public wants to know why targeting occurred and who was involved" and that Cummings’ account "did not provide anything enlightening or contradict other witness accounts."

"The only thing Ranking Member Cummings left clear in his comments today is that if it were up to him the investigation would be closed," Issa said. "Fortunately, the decision to close the investigation is not his to make."

Issa added that he intends to continue to work with  the House Ways and Means Committee Chairman, Rep. Dave Camp (R-Mich.), on a "fact based investigation that fully exposes all relevant facts about IRS efforts to target Americans for their political beliefs."

House Republicans will file a civil suit against Attorney General Eric Holder during the August recess, House Oversight Committee Chairman Darrell Issa, R-Calif., has told NBC News.

House Republicans will file suit in an effort to compel Holder to release documents associated with the failed "Fast and Furious" gun-walking operation.

"We'll be filing a civil case during the break," Issa told NBC, "We will expect a day in court before a federal judge, which we have a 100 percent chance that the judge will hold that these documents should be delivered."

During negotiations between House Republicans and Holder in June, the White House invoked executive privilege on the documents Issa had requested for his investigation. Issa says that a federal judge should find that executive privilege does not apply to the documents he is requesting.

"The idea that you would withhold based on some executive privilege the documents related to a cover up of a crime is absurd, but that's the claim that the attorney general is hiding behind," Issa said.

The House voted on June 28th, 255-67, to hold Holder in contempt of Congress for not turning over documents related to the Fast and Furious operation. During that vote, the vast majority of Democrats walked off the floor of the House in protest of a measure they saw as a political witch hunt.

Soon after the House found Holder in contempt of Congress, the Justice Department penned a letter to House Republicans saying it would not be pursuing the case, stating that "the attorney general's response to the subpoena issued by the Committee on Oversight and Government Reform does not constitute a crime." The DOJ cited the White House invoking executive privilege as a primary reason for not proceeding.

Larry Downing / REUTERS

U.S. Attorney General Eric Holder during a meeting at the White House in Washington, July 26, 2012.

The DOJ's response has left Republicans with few options, according to Issa, who compared the current situation with congressional attempts to retrieve the Nixon tapes during their investigation into the Watergate scandal in the 1970s.

"We're seeking a remedy and the remedy is an order to compel," Issa said. "Nixon didn't respond to Congress, he responded to federal judges, ultimately the Supreme Court, ordering that he had no such privilege to cover up the tapes. And these are no different than the Nixon tapes, we're asking for documents related to a cover up of lying to Congress."