The U.S. Justice Department (DOJ) may have new ammunition in their fight to keep Anthem and Cigna from merging: the companies’ own behind-the-scenes bickering.

The New York Times reported on a legal filing from the DOJ that alleges the in-house attorneys for both companies have exchanged letters accusing the other of violating the terms of the $48 million merger agreement. The DOJ is asking a federal judge to compel the insurers to release the letter, arguing they would “reveal the current state of hostility between defendants,” and call into question the insurers’ claims that the merger would save billions of dollars and improve care.  

“Such efficiencies don’t happen overnight,” the DOJ wrote in its court filing according to the Times. “They require cooperation over months (if not years) to integrate the operations of these multibillion-dollar firms.”

Both Anthem and Cigna declined to comment on the filing, though bickering between the insurers had been reported well before the DOJ sued to block the merger on antitrust grounds.

Anthem’s lawyers have hinted at the tension in court, saying a speedier trial schedule was needed, or else Cigna would exercise its right to back out of the merger beginning on April 30, 2017, collecting a $1.85 billion break-up fee in the process.

For more on DOJ’s filing and how the insurers’ disagreements could undermine their defense in the antitrust trial, click on the link below: