Mike Huckabee on Thursday ripped Mitt Romney for calling on Donald Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE to release his taxes, accusing the 2012 GOP nominee of trying to "sink" the party's current presumptive presidential nominee.

"I supported Romney, just as I will Trump, despite having serious differences with both," Huckabee wrote on his website, adding that he was "especially disappointed" in Romney over the issue.

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"He’s not only trying to sink his own party’s presumptive nominee, but he’s factually incorrect and he’s making the same unfair attack on Trump that was launched against him in 2012," he wrote.

Romney has been calling on Trump to release his tax returns since February, while other Republican candidates were still in the primary race. He reiterated that call on Wednesday, saying it would be "disqualifying" if Trump didn't release his returns. Democrats have also seized on the issue this week.

Romney, who came under fire in 2012 from his political opponents for releasing his tax returns in what they felt was a timely manner, again claimed Trump's refusal to release his returns indicated they included a "bombshell."

Trump said he'd release his returns after an audit ends, though the Internal Revenue Service said in February there's nothing preventing him from releasing his forms.

Huckabee suggested there was nothing to learn from Trump's returns, as the candidate himself has argued, and said it would be a "treasure trove" for the businessman's political opponents "to lift items out of context to make him look shady."

Huckabee also argued it's "an invasion of privacy" for presidential candidates to release their tax returns, writing, "The qualifications for the Presidency are clear-cut, and there are specific financial disclosure forms you must file. But no law requires a candidate to release his or her personal tax forms."

Later in his post, Huckabee admitted, "Early in my political career, I volunteered to release all my tax returns. Why not? I had nothing to hide." However, he said, his political opponents misconstrued them. He said Romney should instead turn his attention to "the 70,000-plus-page tax code."