The chairman of the House Republican campaign arm on Tuesday condemned recent remarks made by Rep. Steve King (R-Iowa) on white nationalism, becoming the highest-profile GOP leader to rebuke the lawmaker to date.

In a tweet Tuesday afternoon, Rep. Steve Stivers (R-Ohio), chairman of the National Republican Congressional Committee, said that King’s “recent comments, actions, and retweets are completely inappropriate.”

“We must stand up against white supremacy and hate in all forms, and I strongly condemn this behavior,” Stivers said in the tweet.

Stivers’s remarks set him apart from the top three House Republican leaders — Speaker Paul D. Ryan (Wis.), Majority Leader Kevin McCarthy (Calif.) and Majority Whip Steve Scalise (La.) — all of whom have declined to criticize King in recent weeks.

King issued a statement on Twitter late Tuesday afternoon in which he denounced “Establishment Never Trumpers” and attacks that he said were “orchestrated by nasty, desperate, and dishonest fake news” and aimed to “flip the House and impeach Donald Trump.”

Rep. Steve King (R-Iowa) speaks at the Iowa Freedom Summit on Jan. 24, 2015, in Des Moines. (Scott Olson/Getty Images)

“Americans, all created equal by God, with all our races, ethnicities, and national origins-legal immigrants and natural-born citizens, together make up the Shining City on the Hill,” he tweeted.

King’s Democratic opponent, J.D. Scholten, said he welcomed Stivers’s comments.

“Last week I issued a challenge for at least one Republican elected official to condemn @SteveKingIA’s recent behavior. I applaud @RepSteveStivers, Chair of the NRCC. Respect,” Scholten said in a tweet.

King has a long history of incendiary remarks on race and immigration throughout his 16 years in Congress. Last year, King was widely criticized after he declared in a tweet that he agreed with far-right Dutch politician Geert Wilders that “our civilization” cannot be restored “with somebody else’s babies.”

But the lawmaker’s actions have drawn increased scrutiny in the wake of Saturday’s mass shooting at a Pittsburgh synagogue. The massacre, in which 11 people were killed, was the deadliest attack on Jews in the United States.

In June, King prompted criticism when he retweeted a message sent by Mark Collett, a self-described “Nazi sympathizer.” King declined to delete the retweet.

Earlier this month, King tweeted his support for Faith Goldy, a white nationalist who was running for Toronto mayor. An editor for the conservative Weekly Standard responded by writing a piece in which he called King “America’s most deplorable congressman.” Ryan, McCarthy and Scalise did not respond to requests for comment from The Washington Post on King’s endorsement.

And last week, it emerged that King had met in August with members of a far-right Austrian party with historical Nazi ties and declared that “Western civilization is on the decline.”

Stivers’s admonition came hours after Land O’Lakes announced that it was withdrawing its support for King. The company had faced calls for a boycott after it emerged that it had made a $2,500 contribution to King’s campaign in June. Tech giant Intel also recently announced in an email to employees that it was ending its support for King in light of his recent comments, Fast Company reported.

The nonpartisan Cook Political Report changed its rating for King’s district Tuesday from “likely Republican” to “lean Republican,” noting that Scholten has vastly outraised King, “in large part thanks to disgusted national donors who view King as a racist.”

Even so, the political handicapper noted that “it’s less clear his views have damaged his political standing back home in northwest Iowa,” where King has been easily reelected in the past and where President Trump won a resounding victory in 2016.

Mike DeBonis, Maura Judkis and Julie Zauzmer contributed to this report.