Mitt Romney on Wednesday said 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’s refusal to release his tax returns should make him ineligible for the presidency.

“It is disqualifying for a modern-day presidential nominee to refuse to release tax returns to the voters, especially one who has not been subject to public scrutiny in either military or public service,” the 2012 Republican presidential nominee wrote on Facebook.

ADVERTISEMENT

“There is only one logical explanation for Mr. Trump's refusal to release his returns: there is a bombshell in them. Given Mr. Trump's equanimity with other flaws in his history, we can only assume it's a bombshell of unusual size,” Romney said.

Romney, who has feuded publicly with Trump, made this claim before as he tried earlier this year to prevent Trump from winning the Republican nomination. He experienced similar attacks during his presidential run in 2012 when Senate Minority Leader Harry Reid Harry Mason ReidSenate Republicans signal openness to working with Biden Mellman: The likely voter sham Bottom line MORE (D-Nev.) charged that Romney had not paid taxes for 10 years.

Romney released his tax returns for two years and a summary of returns dating back to 1990 but drew criticism from Reid and others for not releasing a more thorough accounting.

Trump told The Associated Press he doesn’t plan to release his returns before the November election, saying “there’s nothing to learn from them.”

The Internal Revenue Service issued a statement in February saying nothing prevents Trump from releasing his tax returns after he blamed an audit for his initial refusal to do so.

Trump's campaign released a letter from his attorneys in March saying his returns had been "under continuous examination" since 2002. He has continued to decline calls to release his returns since then.

"I'll do it as fast as the auditors finish," Trump said Sunday on NBC's "Meet the Press."

While releasing tax returns isn’t legally required of presidential candidates, it is customary, and Trump would be the first major candidate to withhold them since 1976, according to a New York Times report.

Democratic front-runner Hillary Clinton Hillary Diane Rodham ClintonWhat Senate Republicans have said about election-year Supreme Court vacancies Bipartisan praise pours in after Ginsburg's death Trump carries on with rally, unaware of Ginsburg's death MORE also called on Trump to release his returns Wednesday, saying “we’re going to find out” why he won’t.