Mark Cuban. AP Photo/Alex Brandon Brash billionaire Mark Cuban took a swing at Donald Trump on Twitter on Tuesday, suggesting that the reason Trump hadn't releasing his tax returns was that the Clintons "made more" money than him.

"Lots of people concerned how much money the Clinton's have made," he tweeted. "More interesting to me they have paid 43mm IN TAXES since 2007."

"I'd bet the 43mm in TAXES the Clinton's paid is not only more taxes than @realDonaldTrump has paid," he continued. "I'd bet they made more too."

Trump has raised eyebrows by repeatedly refusing to release his tax returns, citing an IRS audit that may not be completed before the November election. All major-party presidential candidates since 1976 have released their tax returns.

"It's not a tough argument looking at their taxes and fec filings that the Clinton's are much smarter business people and negotiators," wrote Cuban, who owns the NBA's Dallas Mavericks and stars on ABC's "Shark Tank," adding, "I get offers almost daily (at same $ as clintons) to give speeches Organizations want knowledge and insight. It's a great business."

"Maybe @realDonaldTrump didn't release his taxes become @HillaryClinton paid more in taxes than @realDonaldTrump made in income?" he continued.

Cuban previously was publicly excited about the possibility of a Trump presidency, but he has recently soured to the point of frequently ridiculing the Manhattan billionaire. Earlier in the cycle he even expressed interest in serving as either Trump's or Clinton's running mate — he was not selected by either.