The White House said Republican presidential front-runner Donald Trump's call to ban Muslims from entering the U.S. disqualified him from becoming president. White House press secretary Josh Earnest made the comments during a daily news briefing Dec. 8. (Reuters)

White House press secretary Josh Earnest said Tuesday that GOP presidential candidate Donald Trump's proposal to block all Muslims from entering the United States "disqualifies him from serving as president."

Earnest's condemnation of the Republican 2016 front-runner, which marked his sharpest criticism yet of the New York businessman, included a description of Trump comparing him to "a carnival barker" who engages in ""vacuous sloganeering" and sports "fake hair." The extended exchange with reporters reflected not just White House officials' distaste at Trump's message but their leveraging of a political opportunity to drive a wedge between GOP leaders and their base.

"What Donald Trump said yesterday disqualifies him from serving as president," Earnest said."The question now is about the rest of the Republican Party, and whether they’ll be dragged into the dustbin of history with him."

The press secretary noted that while several GOP elected officials and presidential hopefuls had not embraced the controversial policy proposal, "Today the newly-elected speaker of the House said he would vote for Donald Trump for president if he’s the party’s nominee."

"They should say right now that they will not support him for president," Earnest added.

Speaking to reporters Tuesday morning, House Speaker Paul D. Ryan (R-Wisc.) criticized Trump's proposed ban without naming him, saying, "What was proposed yesterday is not what this party stands for and, more importantly, it’s not what this country stands for."

However Ryan would not say he would refuse to support Trump if he emerged victories from the GOP primaries: “I’m going to support whoever the Republican nominee is, and I’m going to stand up for what I believe in as I do that.”

Earnest said the criticism Ryan and others have made so far are insufficient because they have yet to repudiate Trump's candidacy. "I would say those comments don’t mean that much if they are going to go ahead and vote for him."

"Do they have the courage of their convictions and say they are going to side with the Constitution over Mr. Trump?" he asked.

White House staffers, including political director David Simas, took to Twitter to challenge other Republicans to step forward.

A Republican official, who asked not to be identified in order to discuss internal party deliberations, said in an e-mail that the speaker has unique responsibilities as chair of the GOP convention. "Given the potential for a brokered convention, the speaker’s position as Chairman of the proceedings requires complete neutrality until there is a presumptive nominee," the official said.

Throughout the briefing, Earnest peppered his comments with criticism of everything to Trump's policy proposals--which he called "grotesque and offensive"--to the candidate's physical appearance. At the outset of his remarks, the press secretary said "the Trump campaign, for months now, has had a dustbin of history-like quality to it, from the vacuous sloganeering to the outright lies to even the fake hair, the whole carnival barker routine that we've seen for some time now."

"I guess I was describing why it would be easy for people to dismiss the Trump campaign as not particularly serious. Because he's got a rather outrageous appearance," he said when questioned on his hair comment later. "That's a hallmark of his campaign and his identity, though."

When a second reporter questioned how Earnest knew Trump's hair wasn't real, Earnest retorted, "Uh, I guess I'm happy to be fact-checked."