Updated on December 18 at 5:44 p.m. EST

The Bernie Sanders campaign came out swinging against the Democratic National Committee’s decision to suspend its access to the list of likely Democratic voters after the campaign was accused of improperly accessing Hillary Clinton’s private campaign data.

“We are announcing today if the DNC continues to hold our data hostage and continues to attack the heart and soul of our grassroots campaign, we will be in federal court this afternoon seeking immediate relief,” Jeff Weaver, Sanders’s campaign manager, said at a news conference. “What is required here is a full and independent audit of the DNC’s mishandling of this data, and its security from the beginning of this campaign to the present.”

Weaver followed through on that promise: the presidential campaign filed a lawsuit against the Democratic National Committee Friday night, the Associated Press reported.

Weaver laid the blame squarely at the hands of NGP VAN, the vendor that handles the master file, and the DNC. He said the campaign discovered a similar breach in October, segregated the data, and informed the DNC of the breach. He said the DNC assured the campaign that the problem would be fixed.