House Speaker John Boehner on Thursday staunchly defended his chamber's Benghazi investigation committee after senior Democrats called for it to be disbanded, claiming Boehner's top deputy -- and the favorite to step into the speaker's shoes -- implied in an interview the panel was created to politically damage Hillary Clinton.

House Majority Leader Kevin McCarthy, R-Calif., stirred the Democratic backlash after he seemed to link Clinton's dropping poll numbers to the committee's work.

The comments gave Democrats an opening to reprise allegations the committee is merely a political tool. Rep. Nancy Pelosi, the chamber's top Democrat, said Thursday that the investigation is "unethical" and the panel should be shut down. Pelosi also questioned whether the panel violates House rules forbidding spending taxpayer dollars for political purposes.

But Boehner, without mentioning McCarthy's remarks, fired back and issued a statement saying the panel would keep working.

"This investigation has never been about former Secretary of State Clinton and never will be," he said. "... The members of this committee have worked diligently and professionally to fulfill this important mission and they will continue to do so. ...

"The American people deserve the truth about what happened in Benghazi. That's always been our focus, and that's going to remain our focus."

McCarthy made the comments in an interview Tuesday night with Fox News' Sean Hannity. Describing how he would be different as speaker, McCarthy said he'd be a "conservative speaker that takes a conservative Congress that puts a strategy to fight and win."

He added: "And let me give you one example. Everybody thought Hillary Clinton was unbeatable, right? But we put together a Benghazi special committee, a select committee. What are her numbers today? Her numbers are dropping. Why? Because she's un-trustable. But no one would have known any of that had happened had we not  ..."

Democrats swiftly suggested his comments undermine claims by the committee's leader and other Republicans that the panel is only seeking the truth about the deadly 2012 attacks at a U.S. diplomatic facility in Benghazi, Libya.

"I appreciate Rep. McCarthy finally coming clean and admitting what we have all known all along: that the Benghazi Select Committee was designed and created as a political attack tool to damage a potential Democratic presidential nominee," Rep. Adam Smith, D-Wash., a Benghazi committee member and top Democrat on the House Armed Services Committee, said in a statement.

The comments are causing some turbulence for McCarthy as he seeks to replace the retiring Boehner in the top House post. But the controversy also comes at a critical time for the committee itself as it prepares to question Clinton later this month in a high-profile public hearing.

A spokesman for McCarthy said the Benghazi panel remains focused on getting the facts about the 2012 attacks that led to the death of four Americans, including the U.S. ambassador to Libya.

The Benghazi panel's investigation and an inquiry by the FBI into Clinton's email practices "have nothing to do with politics and everything to do with the consequences of what the former secretary has done and her confusing, conflicting and demonstrably false responses," said Matt Sparks, a McCarthy spokesman.

The Associated Press contributed to this report.