Former acting DNI Richard Grenell slammed Politico on Tuesday over its report that he was joining the Trump campaign, calling it "fake news."

Politico ran a story claiming that Grenell was aiding President Trump's re-election team, specifically in "fundraising and strategy." The reporting was cited by "two people familiar with the matter."

However, after the story was published, Grenell flatly denied Politico's reporting.

"Fake news. Do you even check before writing? What has happened to Washington DC media?!" Grenell reacted to a now-deleted tweet from the Politico reporter who had shared the story.

Following Grenell's tweet, Politico updated its report with his response and reiterated that he "hadn't responded to a request for comment" prior to publication. No editor's note or correction was made.

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Trump campaign manager Brad Parscale also slammed Politico's report.

Here is more proof of #FakeNews. I like @RichardGrenell and we are friends but this story isn’t true. Just more garbage of people making sensational claims," Parscale tweeted.

Despite the denial from Grenell and the Trump campaign, the report was shared across social media, including by the Biden campaign.

"And just like that, @RichardGrenell has been unmasked as the Trump campaign deputy press secretary that he was all along," Biden campaign rapid response director Andrew Bates reacted to the Politico report, which was retweeted by Biden press secretary TJ Ducklo.

A spokesperson for Politico told Fox News, "We stand by our reporting. Though Mr. Grenell failed to respond to multiple requests for comment prior to publication, we encourage him to do so and to detail what specific facts he believes are inaccurate in the story. We will certainly update the story to include them."

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Despite Politico's confidence in its reporting, Grenell doubled down, firing back at its communications vice president Brad Dayspring, who challenged the former acting DNI what specifically was incorrect about its report.

"The entire story isn’t true. And your response is scary - you don’t believe the campaign denial nor mine. But claim you have some anonymous source. Do you realize how ridiculous you sound?" Grenell asked.

"Let’s go point by point. Please state *SPECIFICALLY* what you believe to be untrue. Don't paint in broad strokes, let's have this discussion. Is your next job going to be on the Trump campaign? Yes or no?" Dayspring pressed Grenell.

"No. Delete the story, it’s false," Grenell shot back.

Grenell did not respond to Fox News' request for comment.

Grenell, who previously served as the U.S. ambassador to Germany, caused a political firestorm in Washington, D.C., for a series of declassified documents involving the Russia investigation and the surveillance of former national security adviser Michael Flynn.

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He declassified the list of top Obama officials who had requested the unmasking of Flynn, including former Vice President Joe Biden, former FBI Director James Comey, former DNI James Clapper, former CIA Director John Brennan, former U.N. Ambassador Samantha Power, and former White House chief of staff Denis McDonough.

On his way out as acting DNI, Grenell also declassified the transcripts of Flynn's conversations with Russian ambassador Sergey Kislyak, which prompted the investigation into the former Trump official. They are now in the hands of incoming DNI John Radcliffe, who was just confirmed last week by the Senate.