WASHINGTON -- Steve Rattner, President Barack Obama's former car czar, weighed in on Mitt Romney's tax returns Sunday, arguing that the presumptive Republican nominee took advantage of an especially large number of loopholes.

"If you say to your tax people, as he seems to have done, 'I want every trick in the book. I want to push this to the edge,'" Rattner said during an appearance on "Fareed Zakaria GPS" on CNN. "I will tell you that as a private equity guy, I'm familiar with many of the things that he did. And I know many people who have done many of the things that he did. I do not know anyone who did everything that he did."

"Some of what he did, like the IRA, I have asked fellow private equity guys," Rattner said, referencing the account in which Romney has stored up to $100 million tax-free. "None of us had even known this was a possible trick, if you will. He has pushed the envelope all the way to the edge, to his benefit, and I think that Americans would find that pretty distasteful."

Romney has declined to release multiple years' worth of tax returns, disclosing only those from 2010 and estimates from 2011. Rattner called Romney overly secretive Sunday, speculating that he was attempting to hide more instances of using innovative and questionable accounting tricks.

Rattner, who hails from the world of private equity, has occasionally served as a voice of sympathy for Romney as his business career has come under heavy attack. His comments, then, carry a bit more weight than the average criticism from an Obama ally.

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  • Ron Paul

    "Politically, I think that would help him," Paul said in a interview with <a href="http://www.politico.com/news/stories/0712/78599.html#ixzz20w7ycTBE" target="_hplink">Politico</a>. "In the scheme of things politically, you know, it looks like releasing tax returns is what the people want."

  • Richard Lugar

    "I have no idea on why he has restricted the number to this point," <a href="http://www.cbsnews.com/8301-18563_162-57474352/pressure-mounts-on-mitt-romney-to-release-more-tax-returns/?tag=socsh" target="_hplink">Lugar said</a>.

  • George Will

    "I don't know why... he didn't get all of this out and tidy up some of his offshore accounts and all the rest," Will said on ABC's "<a href="http://www.huffingtonpost.com/2012/07/15/george-will-mitt-romney-bain_n_1674513.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+HP%2FPolitics+(Politics+on+The+Huffington+Post)" target="_hplink">This Week</a>." "He's done nothing illegal, nothing unseemly, nothing improper, but lots that's impolitic."

  • Bill Kristol

    "He should release the tax returns tomorrow. It's crazy," Kristol said on "<a href="http://www.huffingtonpost.com/2012/07/15/mitt-romney-tax-returns_n_1674325.html" target="_hplink">Fox News Sunday</a>." "You gotta release six, eight, 10 years of back tax returns. Take the hit for a day or two."

  • Robert Bentley

    "I just believe in total transparency," Bentley told <a href="http://abcnews.go.com/blogs/politics/2012/07/gop-governor-calls-on-mitt-romney-to-release-additional-tax-returns-and-show-he-has-nothing-to-hide/" target="_hplink">ABC News</a>. "In fact, I was asked today that question -- do you think that Governor Romney should release his tax returns? And I said I do. I said, I release my tax returns. I may be the only public official in Alabama that does, but I release mine every year and I just believe that people should release their tax returns. And if you get them out and just get past that, it just makes it so much easier."

  • Haley Barbour

    When asked on "<a href="http://www.nationaljournal.com/2012-presidential-campaign/barbour-romney-should-release-more-tax-returns-20120710" target="_hplink">The Situation Room</a>" if Romney should release more returns, Barbour said, "I would. But should it be an issue in the campaign? I don't think it amounts to diddly."

  • Michael Steele

    "If there's nothing there, there's no 'there' there, don't create a there,'" Steele said on MSNBC.

  • David Frum

    "Tax returns the next problem. Releasing returns under pressure: more weakness, more pain," Frum <a href="https://twitter.com/davidfrum/status/224509505973661696" target="_hplink">tweeted</a>.