The decision, revealed during a recent interview, threatens to put the front-running candidate, who is one of the wealthiest men ever to run for the White House, on the back foot heading into the start of the 2012 primary season, which begins with this weekend's Iowa Caucuses.

Almost every would-be President since the 1970s has published their tax return, but Romney announced that he intended to forego that opportunity during an interview with Chuck Todd of MSNBC. He did not seek to justify the decision, but said merely: "I don't intend to release the tax returns. I don't."

The comments were edited out of the interview before broadcast last week, but emerged during extended footage aired at the weekend. Asked about the issue on the campaign trail, Romney added: "We follow the tax laws, and if there's an opportunity to save taxes, we, like everybody else in this country, will follow that opportunity."