Former Hillary Clinton Hillary Diane Rodham ClintonHillicon Valley: FBI chief says Russia is trying to interfere in election to undermine Biden | Treasury Dept. sanctions Iranian government-backed hackers The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters FBI chief says Russia is trying to interfere in election to undermine Biden MORE campaign press secretary Brian Fallon on Saturday called President Trump's White House press secretary Sean Spicer a "failure."

Fallon's criticism came after Spicer slammed the media during his first appearance behind the lectern at the White House briefing room on Saturday, defending Trump's inaugural crowd size.

"This was the largest audience to ever witness an inauguration, period, both in person and around the globe,” Spicer said.

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Fallon tweeted shortly after the press conference, writing, "Sean Spicer lacks the guts or integrity to refuse orders to go out and lie. He is a failure in this job on his first full day."

Sean Spicer lacks the guts or integrity to refuse orders to go out and lie. He is a failure in this job on his first full day. — Brian Fallon (@brianefallon) January 21, 2017

Political observers speculated Fallon would have served as White House press secretary had Clinton won.

The statement by Spicer echoed the words of Trump himself, who boasted Saturday about the size of the crowd that witnessed him take the oath of office.

"I get up this morning and I turn on one of the networks and they show an empty field. I said wait a minute, I made a speech, I looked out, the field was, it looked like a million, a million and a half people,” the president said.

Spicer repeated Trump’s claim, saying “all of this space was full when the president took the oath of office.”