Conservative commentator Ben Shapiro said Friday that impeachment "should be on the table" if President Trump or one of his appointees ends special counsel Robert Mueller's investigation into Russian interference prematurely.

Shapiro, the founder and co-editor of The Daily Wire, appeared on HBO's "Real Time With Bill Maher," where he said he doesn't believe Trump colluded with Russia in the 2016 election. Shapiro said he's waiting to see evidence suggest otherwise.

"When the evidence comes out I'm happy to go with the indictments. Criminal activity is criminal activity," he said.

"I'm happy to wait for the Mueller indictments," he added. "If they come down and they target Trump, I'm happy to see him impeached. But I need to see evidence."

Maher argued that Republicans don't want any type of incriminating report to come out in the special counsel's investigation, which is why they've accused Mueller of bias and have recently ratcheted up their attacks on Deputy Attorney General Rod Rosenstein, who oversees the investigation.

Shapiro said attacks on Rosenstein are less concerning, since Mueller could still be left to do his job under a different deputy attorney general. However, he said, if Rosenstein's hypothetical replacement ended the probe, it would be a problem.

"If he throws it in the trash or quashes the Mueller investigation then, yes, impeachment should be on the table," Shapiro said.

The president has frequently decried the Mueller probe as a "witch hunt" and a "hoax." His Republican allies have accused the Department of Justice of being biased against the president.

Mueller, meanwhile, has indicted or obtained guilty pleas from four former Trump associates in his investigation, and filed charges against 13 Russian nationals.