Billionaire investor Mark Cuban is escalating his criticisms of Donald Trump, the Republican party's presumptive presidential nominee, and ribbing his fellow businessman over getting "stupider" as his White House campaign charges on.

"You know what? It's rare when you see somebody get stupider before your eyes, but he's really working at it," Cuban told the entertainment show "Extra" in an interview published Tuesday. "And so you've got to give him credit. It's not an easy thing to do, but he's accomplished it."

Cuban, who has previously bashed Trump on a host of issues, elaborated: "Let's look at it this way," he told "Extra" host Renee Bargh. "Name one good deal he's done."

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"I can't," Bargh replied.

Cuban shot back: "Neither can he."

"When he talks about his great renegotiations, they're renegotiations," said Cuban, co-star of investment-based reality television show "Shark Tank" and owner of the Dallas Mavericks. "So tell me if you think this is a good deal: I lose four casinos, they go out of business, but I'm really good at renegotiating the debt of my companies that have already gone out of business. You'd get kicked out of 'Shark Tank' so fast it'd make your head spin."



Cuban isn't far off base when it comes to characterizing Trump's success at renegotiating debt -- even according to the presumptive GOP nominee himself.

In an interview with "CBS This Morning" that aired Wednesday, Trump dubbed himself the "king of debt."

"I call myself the king of debt," he told host Norah O'Donnell. "I'm great with debt. Nobody knows debt better than me."

He explained further that he's "made a fortune by using debt" in his business transactions.

"If things don't work out, I renegotiate the debt," Trump said. "I mean, that's a smart thing, not a stupid thing."

Cuban, in his own interview, continued his tirade against Trump with knocks on the real estate mogul's ability to learn about policy issues.

"At some point, you've got to start learning and understanding the issues, you know?" Cuban said. "Donald has been in this a year and you don't look at him and say, 'Wow, he's gotten so much smarter about this topic or that topic.' In fact, you know, you look at him and say, 'What the hell are you talking about?'

"That's not good for America," Cuban added, noting that he doesn't usually become involved in politics. "But now, it's so crazy that if somebody in the middle doesn't speak up, some topics don't get covered."