The IRS admitted last week that it was targeting conservative groups with the words "tea party" and "patriot" in their names, often probing to ensure these groups qualified for tax-exempt status.

"I am confident that President Obama will work to get to the bottom of this and ensure that all those responsible for wrongdoing are held fully accountable, and I urge him to begin this review immediately," Cicilline added.

A handful of Democratic senators have criticized the IRS for discriminating against groups based on ideology, but very few House Democrats have. Of the 16 Democrats on the House Way & Means Committee, which has jurisdiction over tax legislation, none of them had issued a formal statement on the controversy as of Monday morning.

Ways & Means Chairman Dave Camp (R-Mich.) has said he'd hold a hearing on the issue later this month. Rep. Charles BoustanyCharles BoustanyDemocrats, Republicans must work together to advance health care Lobbying World Former GOP rep joins K Street lobbying firm Capitol Counsel MORE (R-La.), who chairs the subcommittee on Oversight, has demanded information from the IRS on its targeting of conservative groups.