The IRS “improperly withheld” documents to prevent a government transparency group from commenting on the agency’s new rules restricting the political activity of nonprofit groups, according to a new Freedom of Information Act (FOIA) complaint.

The group Cause of Action requested four sets of communications between the IRS and administration officials to ensure that political bias did not factor into the design of the new rules. But the IRS delayed the release of the documents until after the period to make public comments on the new rules closes Thursday, according to an amendment to Cause of Action’s existing lawsuit against the IRS.

“By letter dated January 30, 2014, the IRS informed Cause of Action that its FOIA request had been received… However, the IRS advised that it would be unable to complete the processing of the request even by February 13, 2014. Instead, the IRS estimated that its final response would not be forthcoming until May 16, 2014,” according to the complaint.