The political watchdog organization Common Cause filed a complaint with the Internal Revenue Service on Monday challenging the tax-exempt status of the conservative American Legislative Exchange Council, reports Bloomberg.

In a statement, the president of Common Cause, Bob Edgar, accused the council, known as ALEC, of violating its 501(c)(3) designation by lobbying state lawmakers and said it should be required to pay back taxes. “ALEC is a corporate lobby front group masquerading as a public charity,” Mr. Edgar said.

The council, a network of corporations and mostly Republican state legislators, has come under fire from liberal and civil-rights groups for backing “stand your ground” self-defense laws and voter-ID measures. Last week the council announced it would no longer take an advocacy role in public-safety and social-policy issues.

Alan P. Dye, the organization’s legal counsel, said the Common Cause complaint was ideologically motivated. The recent attacks, he said, “are based on patently false claims being made by liberal front groups that differ with ALEC on philosophical terms.”