White House Press Secretary Sean Spicer dramatically exited the White House press briefing on Tuesday, his first day back at the podium since the president returned from his overseas trip, as reporters hurled questions at him about the administration's assault on anonymous sourcing and fake news.

Spicer abruptly ended his Tuesday afternoon briefing after three news outlets the president has called 'fake news' and 'the enemy of the American people' pressed the Trump spokesman on his claims and demanded he provide a list of stories the White House believes to be false.

'What I'm telling you is that the reason the president is frustrated is the perpetration of false narratives, the use of unnamed sources over and over again about things that are happening that don't ultimately happen and I think that is troubling,' Spicer said in his final word on the topic.

Packing up, Spicer told the room, 'thank you, guys, very much,' and left amid yelling, and some booing.

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White House Press Secretary Sean Spicer dramatically exited the White House press briefing on Tuesday, his first day back at the podium since the president returned from his overseas trip, as reporters hurled questions at about the administration's assault on anonymous sourcing and so-called fake news

The dispute began at the top of the 20 minute question and answer session that centered on an article that said Jared Kushner, the president's son-in-law, had attempted to set up a back channel with Russia, and reports that have claimed the White House is on the verge of a staff shake up

The dispute began at the top of the 20 minute question and answer session that centered on a Washington Post article that said Jared Kushner, the president's son-in-law, had attempted to set up a back channel with Russia, and reports that have claimed the White House is on the verge of a staff shake up.

Giving the Post the first crack of the bat on Tuesday, a reporter for the outlet asked Spicer if the president knew about the effort to set up a back channel when it was happening.

Spicer told the Post's Phil Rucker, 'I'm not going to get into what the president did or did not discuss. What your question assumes is a lot of facts that are not substantiated with anything but anonymous sources that are so far being leaked out.

'You're asking if he approves of an action that is not a confirmed action,' Spicer added...Your question presupposes facts that have not been confirmed.'

White House officials cast a back channel like the one Kushner was said to have floated to the Russians as normal in weekend appearances - but they did not confirm that an exchange of that nature had happened.

The president suggested that the conversation had occurred when he retweeted a Fox News story Tuesday morning on the incident.

The Fox story leaned on an anonymous source who said that the topic did come up, but it was the Russians, not Kushner, who suggested a back channel. The purpose of a private line would have been to talk about Syria, Fox's source said.

Trump on Sunday said the stories that use anonymous sources are 'fake' and it's 'very possible' the people journalists say they are quoting do not exist. His tweet on Tuesday endorsing the Fox article flew in the face of that claim.

Spicer suggested during a back and forth with DailyMail.com, immediately after he rebuffed the Post, that Fox's anonymous source was more reliable than the Washington Post's the latter's report was based on a dossier that most news outlets refused to print when it contents could not be verified.

'The dossier that is largely the basis of this has been largely discredited in the first place. Most of the publications here even refused to publish it in the first place. So I'm not going to get into confirming stuff, there's an ongoing investigation,' he rebutted.

Spicer abruptly ended his Tuesday afternoon briefing after three news outlets the president has called 'fake news' and 'the enemy of the American people' demanded that he provide a list of stories the White House believes to be false

The Post said in its original report that the information it received came in the form of a letter. It sat on it for months as it worked to confirm the details of Kushner's meetings with the Russian ambassador at Trump Tower in December.

As the briefing unfolded, Spicer continued to hammer anonymous sources that have appeared in numerous unflattering articles on the White House and its operations.

'I think he is very pleased with the work of his staff. I think that he is frustrated, like I am, and some of the others, to see stories come out that are patently false. To see narratives that are wrong,' Spicer told the AP's Catherine Lucey. 'To see "fake news." When you see stories get perpetrated that are absolutely false, that are not based on fact, that is troubling and he's rightly concerned.'

It was then that CNN's Jim Acosta jumped in to ask for an example.

Spicer brought up the case of a BBC reporter who claimed that Trump was not wearing his earpiece during a discussion with the Italian prime minister.

'Someone from the BBC and ultimately an incoming reporter from the New York Times retweeted that the president was being rude by disrespecting the Italian prime minister,' Spicer said, 'when in fact you all and everyone in the meetings that we sit in watched the president with the one earpiece that's been used by other presidents.'

DO AS I SAY NOT AS I DO: Trump on Sunday said the stories that use anonymous sources are 'fake' and it's 'very possible' the people journalists say they are quoting do not exist. His tweet on Tuesday endorsing a Fox article that used one defending Jared Kushner flew in the face of that claim

Spicer said he saw the reporter 'who is now joining the New York Times push out and perpetuate, with no apology' fake news.

At that point, the New York Times' Peter Baker interjected to say that Spicer was blowing up one tweet from the widely-covered trip.

'With all due respect I was asked to give an example and I did. I gave an answer to Jim,' Spicer said. 'I didn't come here with a list of things.'

A moment later CBS News' Chip Reed joined in, turning the conversation back reports on the White House's staffing and messaging problems.

'And now you want to go back to that,' Spicer replied testily.

Trump has called the Times, CBS and CNN 'fake news' and 'the enemy of the people' in the past. He decried the anonymous sourcing news outlets have used in reports on his administration as 'fake news' in a set of tweets on Sunday.

'Whenever you see the words 'sources say' in the fake news media, and they don't mention names....,' he said, '...it is very possible that those sources don't exist but are made up by fake news writers. #FakeNews is the enemy!'

With the room of reporters in revolt over the White House's claims, Spicer ended his briefing and dashed on Tuesday afternoon as reporters groaned and shouted at him to come back.

'Sean, come on!' one journalist hollered at him at the end.