A Washington federal judge excoriated a U.S. Justice Department lawyer Thursday for keeping him “in the dark” about the consummation of CVS Health’s $69 billion acquisition of Aetna Inc. and urged the companies to wait for a final judgment on the deal before integrating their operations.

U.S. District Judge Richard Leon, appearing livid at times, accused the Justice Department and the two companies of treating his antitrust review of the acquisition as a “rubber stamp operation.” And he expressed concern about how the integration of CVS and Aetna, which completed their merger Wednesday, would be unwound in the event that he rejects their merger.