BPB, the world's biggest plasterboard manufacturer, repeated its view that a hostile takeover bid from French building material group Saint-Gobain undervalued the British company.
Saint-Gobain announced earlier it had received acceptances of just 0.88 percent after the first closing day of its 3.6-billion-pound (5.35-billion-euro, 6.57-billion-dollar) takeover offer.
The French company also announced an extension to its offer until October 30.
"This very low level of acceptances endorses the board's view that Saint-Gobain's offer fundamentally undervalues BPB," the British group said in an official statement to the London Stock Exchange.
The statement added that BPB's board "strongly advises shareholders to continue to reject Saint-Gobain's offer and not complete any form of acceptance".
Saint-Gobain is bidding 720 pence a share for BPB but many believe the bid is pitched too low.
BPB shares have remained stubbornly above Saint-Gobain's offer price and analysts widely agree that the French group will have to raise its offer if it is to win control.
Saint-Gobain on August 31 set BPB shareholders a deadline of September 30 for acceptance of the offer, which according to the French company carries a 40.5-percent premium to BPB's closing share price on July 20 -- the last day prior to the launch of its bid.