NEW YORK (CNNMoney.com) – In response to recent criticism of the IRS from the nation's taxpayer advocate and lawmakers, IRS Commissioner Mark Everson said Tuesday he has ordered a review of the IRS program that freezes refunds of taxpayers suspected of fraud.

"We will announce plans ... to institute notification procedures as well as significant processing improvements to minimize the number of taxpayers whose refunds are frozen unnecessarily," Everson said in a statement.

Earlier this month in her annual report to Congress, National Taxpayer Advocate Nina Olson told lawmakers that the IRS was withholding hundreds of thousands of refund requests it suspected of being fraudulent for up to 8 months without informing taxpayers their refund claims were under review.

A sample study by her office found that 66 percent of taxpayers in that situation ultimately received their refund.

The IRS noted that the Questionable Refund Program holds less than 1 percent of the 100 million returns claiming refunds every year. Of those held, about 200,000 are held longer than one week, and many are held for months or years.

Taxpayers often are not notified their refunds are being held "because some of these returns are subject to additional criminal investigation," the agency said in the statement announcing Everson's decision.

The most typical fraudulent refund claim involves false income and withholding or false Earned Income Tax Credit claims of up to $4,400, the agency said.

"Claiming fraudulent refunds ultimately undermines the integrity of the tax system, but I believe that appropriate notification should be given when refunds have been frozen," Everson said. "Honest taxpayers expecting a refund deserve to be treated fairly."