 -- Former President Bill Clinton is defending Democratic attacks on Mitt Romney's personal finances and describing himself as "perplexed" and "surprised" that the Republican standard-bearer hasn't released more of his tax returns.

"I am a little surprised that he only released a year's worth of tax returns," Clinton said in an interview with NBC's Today Show.

"That's kind of perplexed me, because this is the first time in, I don't know, more than 30 years that anybody running for president has only done that," he said. President Barack Obama's campaign forwarded Clinton's comments to reporters.

Clinton defended the Obama campaign's increasingly strident attacks on Romney's personal finances—notably the former Massachusetts governor's now-closed Swiss bank account, his holdings in the Cayman Islands—saying those issues are relevant to the election.

"Just as relevant as the going over my record as governor got when I ran for president," he told NBC, underlining that Romney has put his vastly successful history as an investor "at the forefront" of his campaign. "He's said basically, 'I'd be a better president because I know how to create jobs 'cause that's what I did." And he's going to take credit for running a successful Olympics, for example. So when all your work life before you run for president is relevant. I think that will be relevant," Clinton said.

Did Romney put some of his vast fortune overseas to minimize his tax burden? "The public ought to know that," Clinton said.

"The voters can make up their own mind about whether they think it's a good thing for a person who wants to be president to minimize his own tax liability by putting the money in overseas tax shelters," Clinton said.

Both the Obama and Romney campaigns have used the former president's words to their advantage. In fact, Team Romney on Friday worked Clinton into a defense of the Republican candidate's time at Bain Capital, noting that the Democratic two-termer had praised his "sterling business career."