NEW YORK (Reuters) - The Internal Revenue Service is planning a "comprehensive review" of its embattled whistleblower program to improve the speed and quality of its decisions, an agency official said in a June 20 memorandum.

The IRS will work with "internal and external shareholders" to produce a set of expectations to speed up the evaluation and payment of whistleblower claims, IRS Deputy Commissioner Steven Miller wrote in a memorandum posted on the agency's website, first reported by Bloomberg News.

As part of the review, the IRS will set up new timelines for the program, the memorandum stated. For instance, claims received by the whistleblower office will be evaluated within 90 days of receipt. Debriefings of whistleblowers will also be "the rule, not the exception," Miller wrote.

The IRS whistleblower office drew criticism in May from the agency's watchdog, the Treasury Inspector General for Tax Administration (TIGTA). In a report, TIGTA said the IRS whistleblower program may produce inaccurate data while pursuing cases and that deadline goals are not strong enough.

Republican Senator Charles Grassley, who wrote 2006 legislation updating the IRS whistleblower program, said the TIGTA report was evidence that "the IRS isn't serious about processing whistleblower claims in a timely way."

The IRS said it has paid out awards in fiscal 2011 without giving details. In fiscal 2010, the most recent year where data was available, the IRS paid $18.7 million in rewards and collected $464.7 million in taxes stemming from whistleblower claims.

Grassley said in an April 30 letter to IRS that since last September he has heard from whistleblowers complaining their claims have not been progressing at the IRS.