White House Press Secretary Sean Spicer is set for what is sure to be a testy briefing with the press corps Monday after he lambasted the media at an unusual late-Saturday appearance over their reporting on inauguration crowd sizes – while making a series of questionable assertions of his own.

His first full-scale White House briefing is set for 1:30 p.m. ET.

Two days earlier, Spicer summoned the press to the briefing room to excoriate the media for allegedly underplaying President Trump’s inauguration turnout in what he described as a “shameful” attempt to minimize enthusiasm for the new president. Spicer also used the briefing to condemn a reporter’s erroneous claim, since retracted, that a Martin Luther King Jr. bust was removed from the Oval Office.

“We’re going to hold the press accountable,” Spicer said.

But in making his case, Spicer on Saturday incorrectly cited statistics from the Metro transit system to suggest Trump’s inauguration attendance was bigger than that of then-President Obama’s 2013 inauguration.

And he made the sweeping claim, “This was the largest audience to ever witness an inauguration, period, both in person and around the globe.”

Counting spectators in Washington Friday and viewers – watching on television and online – around the world, it is possible Friday’s inauguration had the biggest global audience. But such comprehensive statistics are not available, and the claim cannot be verified. Further, there is little question that Obama’s 2009 inauguration drew a much bigger in-person crowd than Trump’s ceremonies on Friday – based on aerial photography, Metro ridership statistics and other factors.

Trump adviser Kellyanne Conway faced tough questions on Sunday’s “Meet the Press” on NBC News, as she claimed Spicer used “alternative facts” to challenge the media.

White House Chief of Staff Reince Priebus defended Trump and Spicer over their media criticism, saying on “Fox News Sunday” there is an “obsession by the media to delegitimize this president.”

“We are not going to sit around and let it happen,” Priebus said.

Ari Fleischer, former press secretary for then-President George W. Bush, told “Fox & Friends” on Monday that the White House “should push back” on efforts to delegitimize Trump.

“But do it on high ground, not on shaky statistics,” he said.

Fleischer said the complaint about erroneous reporting on the MLK bust was a “legitimate fight.”

But he questioned “why they picked a fight over the size of the crowd,” speculating: “This is where Donald Trump must have said to Sean, ‘Get out there, fix this’ … and Sean felt the squeeze and felt the pressure that the president can impose on him.”