GOP Rep. Justin Amash stepped down from the ultra-conservative House Freedom Caucus on Monday night.

"I have the highest regard for them, and they're my close friends," Amash told CNN. "I didn't want to be a further distraction for the group."

The move comes after Amash ignited a firestorm within his own party by calling for President Donald Trump's impeachment last month.

Though his stance was viewed favorably by many in the public, it prompted Trump allies and several top Republicans to disown him.

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Michigan Rep. Justin Amash stepped down from the House Freedom Caucus on Monday night, CNN reported.

"I have the highest regard for them, and they're my close friends," Amash said. "I didn't want to be a further distraction for the group."

The move comes after the lawmaker ignited a firestorm by being the first Republican to call for President Donald Trump's impeachment last month.

He said he made his decision after reading the former special counsel Robert Mueller's report on the Russia investigation, which examined Russia's interference in the 2016 US election and whether Trump sought to obstruct justice in the inquiry.

Amash wrote on Twitter at the time that he came to his conclusion "only after having read Mueller's redacted report carefully and completely" and reviewing relevant testimony and materials.

Read more: A Republican congressman just became the first in his party to call for Trump's impeachment

Amash also sharply criticized Attorney General William Barr's handling of Mueller's report, the way it was portrayed to the public, and his subsequent attempts to sugarcoat Mueller's findings in what many saw as an effort to shield Trump.

At a town hall shortly after making his comments, Amash said "a lot of" congressional Republicans agree with him that Trump should be impeached, but won't say it publicly.

Amash's remarks were viewed favorably by much of the general public; indeed, a majority of Americans in an INSIDER poll agreed with the Michigan congressman that Trump committed impeachable offenses.

But he faced a lot of heat from members of his own party, many of whom disowned him after he came out against the president.

House Minority Leader Kevin McCarthy called Amash's decision a plea for attention during an appearance on Fox News' "Sunday Morning Futures."

"You've got to understand Justin Amash. He's been in Congress quite some time," McCarthy said. "I think he's asked one question in all the committees that he's been in. He votes more with Nancy Pelosi than he ever votes with me. It's a question whether he's even in our Republican conference as a whole."

The move also prompted Michigan State Rep. Jim Lower to launch a primary challenge, citing Amash's claims as the catalyst.

But the GOP response to Amash was predictable.

Just a few weeks before Amash spoke out against Trump, a media report revealed Sen. Richard Burr, the Republican chairman of the Senate Intelligence Committee issued a subpoena to Donald Trump, Jr. The move infuriated Trump's allies and prompted Republicans to turn on a senator they had previously championed as a calculated leader during tense investigations.