The Romney campaign disputed the findings of a study released Wednesday that found that the Republican candidate's tax plan would raise taxes on middle- and lower-income earners while lowering the overall tax burden on the wealthiest Americans.

"The study does not account for important aspects of Gov. Romney’s pro-growth plan," said Romney spokeswoman Andrea Saul.

A Romney policy adviser who is not authorized to talk to the press provided more details. The aide wrote in an email that the study by the Tax Policy Center does not include the economic growth that would result from the lowering of the corporate tax rate and from cutting the size of government over the next decade.

The study said that Romney's plan would shift at least $86 billion away from higher-income earners onto lower- and middle-income earners.

But the Romney campaign said that by ignoring the Republican's intent to lower the corporate tax rate from 35 percent to 25 percent, the study "discredits the TPC immediately" because the study is "based on flawed assumptions."

"A reduction in the corporate income tax, for example, will directly translate into higher wages for workers," the policy adviser said. "This increase in wages for workers will increase individual income tax receipts; a factor not taken into account at all when TPC made its assumptions about the nature and level of base broadening which would be needed in order to achieve revenue neutrality."

The Romney adivser cited a Tax Foundation study that said that a 10 percent cut in the corporate rate would raise wages by 9 percent.

The TPC study also did not include spending cuts in its analysis of Romney's plan.

"Ignoring the spending reductions made in the Romney economic plan also discredits the TPC analysis as it ignores the impact of economic growth from spending restraint," the adviser said.

The authors of the TPC study said that if they counted spending cuts in their analysis it would likely make Romney's plan "more regressive because government spending tends to benefit low- and middle-income households more than tax preferences do."

UPDATE: 4:15 p.m. -- The TPC report addressed so-called "dynamic scoring" that some economists say helps tax cuts pay for themselves in increased economic growth and resulting higher tax receipts.

Using a model presented in the past by Romney economic adviser Greg Mankiw, the TPC study said that if economic growth occurred at the rate they predicted, Romney's plan would still shift about $33 billion (instead of $86 billion) away from high earners and onto lower- and middle-income earners.

"Thus even generous assumptions regarding the ability of tax cuts to partially pay for themselves does not change the basic qualitative results," the TPC study concluded.

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  • Ron Paul

    "Politically, I think that would help him," Paul said in a interview with <a href="" 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="" 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="" 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="" 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="" 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="" 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="" target="_hplink">tweeted</a>.