(CNN)
Paul Manafort.

CNN anchor Jake Tapper confronted one of Donald Trump's top advisers over Trump's alleged penchant for posing as his own spokesperson during calls with reporters.

The Washington Post published audio Friday of a 1991 call between a People magazine reporter and a supposed Trump spokesperson named John Miller, an alias Trump has admitted to using.

Speaking with the same cadence and accent as Trump, Miller defended Trump by laying out frank details of Trump's divorce from Ivana Trump, his first wife.

In a Sunday interview on CNN's "State of the Union," Tapper played the audio for Trump convention manager Paul Manafort and pressed him about why the campaign was refusing to admit that the presumptive Republican frontrunner was on the call.

"Is the campaign seriously claiming that's not Mr. Trump?" Tapper asked.

Manafort countered that he could not understand the tape, and he criticized reporters for following stories that are decades old.

"I can barely understand it. If Donald Trump is saying it's not him, I believe it's not him," Manafort replied.

He continued: "I don't even know the relevance of this, other than that it's 25 years old."

When Tapper pushed Manafort to answer whether he believed the phone calls represented a "character issue," Manafort denied Trump posed as someone else during the call. He said it was natural for spokespeople to assume the language of their bosses.

"The issue is, I think — here you have a man in his 40s allegedly acting as his own public-relations agent, bragging about his exploits with women while married to Ivana Trump, the mother of his three children. It speaks to a kind of character issue, don't you think?" Tapper said.

"But the tape has not proven that it's him," Manafort said. "The justification for the tape is words that are on that tape are words Donald Trump uses. I've been working with Donald Trump for six weeks. I use the words he uses. I'm not the person on that tape."

Over the last several days, Trump repeatedly denied he was the voice on the audio resurfaced by The Washington Post.

"It was not me on the phone," Trump told NBC's "Today" on Friday. "And it doesn't sound like me on the phone, I'll tell you that. And it was not me on the phone."

Even before Friday's Washington Post report, however, Trump's alleged calls to reporters posing as a spokesperson were well-known among many of the New York City reporters who covered the presumptive frontrunner's real-estate deals and personal life.

Trump biographer Michael D'Antonio told Business Insider last year that Trump frequently posed as a spokesperson named John Barron. "Barron" would call reporters to defend Trump's controversial real-estate decisions and often described Trump's personal life in startlingly frank terms.