Trump's allegations came as a television network friendly to his administration said that the material that Comey leaked to a friend to be shared with the media contained classified information.
"James Comey leaked classified information to the media. That is so illegal!" Trump tweeted.
According to The Hill newspaper, more than half of the memos that Comey wrote as personal recollections of his conversations with Trump about the Russian investigations have been determined to contain classified information.
In a Congressional testimony last month, Comey said he considered those as his personal documents.
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Comey said that he considered the memos to be unclassified.
Trump also retweeted a criticism about the mainstream media.
"The mainstream media is neglecting their duty to represent the public. They've failed to represent half of the country," Trump retweeted this tweet of Carrie Sheffield, founder of Bold.
Trump last month had said that he did not have recordings of his meetings with Comey, after weeks of speculation that the Republican billionaire leader himself fueled.