Washington (CNN) A former Forbes reporter claims that Donald Trump, before he was president, pretended to be a Trump Organization executive speaking on Trump's behalf and then lied about his wealth in order to crack the Forbes 400 list.

"He figured out what he had to do in order to deceive me and get onto that list. And he did it very well. And he maintained that persona of just sort of talking about his assets without any sense of debt and lying about it," Jonathan Greenberg said in an interview Friday on CNN's "New Day."

Greenberg broke the news in a Washington Post story. He wrote that when he was compiling the magazine's list of the richest people in America in the 80s, Trump had called him posing as "John Barron," a purported executive with The Trump Organization.

Greenberg said Trump's actual net worth at the time as a real estate developer was less than $5 million, though the magazine had listed it as $100 million for its first-ever Forbes 400 list.

"He should never have been there in the first place," said Greenberg, who provided an audio recording of a phone call between him and "Barron" that he recently discovered to CNN.

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