A former head of the Internal Revenue Service’s nonprofit division has written a complaint to the tax agency questioning the charity status of the conservative legislative group ALEC, the Center for Public Integrity reports.

Marcus Owens, now a tax attorney in private practice, penned the 30-page complaint filed June 18 by Clergy VOICE, a coalition of Ohio ministers. The letter claims that ALEC, the American Legislative Exchange Council, engages in impermissible lobbying on behalf of business and Republican interests and seeks its members’ “private benefit” ahead of any educational or social interest.

The letter follows complaints by the political watchdog group Common Cause and liberal activists that ALEC violates its 501(c)(3) charity designation by writing model state bills and strategizing with legislators to pass them.

ALEC leaders have consistently maintained that the group is a bipartisan research group, saying attacks on its work are politically motivated.