Candian outfit Vincor International has taken out a newspaper advert in large print warning shareholders: "Do not tender your shares to Constellation's inadequate offer."
Vincor's board, meanwhile, has removed a shareholder rights plan that could have acted as a so-called poison pill to help halt Constellation's advances.
"Following discussions with major shareholders, the board of Vincor firmly believes that Constellation's C$31 [per share] offer will be rejected." The board has persistently accused Constellation of "grossly undervaluing" Vincor's growth prospects.
Constellation's hostile cash takeover bid runs out on 28 November. The group, one of the world's biggest branded wine firms, piled on the pressure this week by announcing that Canadian competition authorities had approved the deal.
"Constellation Brands does not expect to encounter any regulatory barriers to close the transaction to acquire Vincor," it said, adding that it had made unspecified commitments under the Investment Canada Act to make sure the deal would benefit Canada as a whole.
The US group recently lost its cool amid rumours Vincor had given out financial information to other potential bidders.
"If Vincor has provided information to any other parties, we are entitled to the same information as any other bidder," said Constellation chairman Richard Sands.
Vincor retaliated by saying that it would hand over information if Constellation offered an "acceptable price".
Sands himself has said that Constellation "would be prepared to offer a higher price", because "this initiative is a high priority for us, and we are committed to making this combination a reality".
That may now be the only option, assuming Constellation still wants the deal.
Sands recently told analysts in the US that Vincor was not a "must-have" acquisition for Constellation. He also said the group did not need to buy other businesses to strengthen its own, after analysts questioned whether Constellation had used bolt-on acquisitions to hide weak organic growth.
Constellation announced it would focus both on Vincor's domestic and international trade and maintain "virtually the same management teams" at most of Vincor's facilities, if the takeover is successful.