The National Association of Chain Drug Stores and the National Community Pharmacists Association are taking what is already an intense lobbying battle to court. The two groups today filed a lawsuit to stop the proposed merger between pharmacy benefit firms Express Scripts Inc. and Medco Health Solutions.

The lawsuit was filed in the U.S. District Court for the Western District of Pennsylvania.

The plaintiffs in the case say the merger would hurt consumers. All sides have been vigorously marshaling supporters on Capitol Hill and have engaged in high-dollar issue advocacy campaigns in recent weeks.

The Federal Trade Commission, tasked with evaluating the merger, has not yet decided whether it will give it a green light. But executives with NACDS and NCPA said the court case would not stop their lobbying effort or take away resources from their effort at the FTC.

The merged company “would leave one clear loser, and that’s the American people,” said NCPA CEO B. Douglas Hoey in a conference call today with reporters.

Don Bell, NACDS senior vice president and general counsel, added on the call that the combined company would create a “huge new middleman” that would stand between patients and their medications.

A spokesman for Express Scripts declined to comment.

The plaintiffs further allege that the combined company would reduce patients’ access to prescription drugs, that it would reduce competition for pharmacy benefit management services and for speciality pharmaceuticals and that it would result in higher prices for consumers.

A press release announcing the lawsuit noted that 76 Members of Congress have written to the FTC raising concerns about the merger, and the heads of the two associations said they would continue to “engage” with Capitol Hill.