Saint-Gobain, the French materials group, is expected to increase its bid for UK plasterboard maker BPB to £3.8bn.

Saint-Gobain had offered to pay 720p a share – a level that the BPB board claimed undervalued the company. It had now raised that figure 5% to 760p a share.

So far the battle between the materials firms has been acrimonious, with BPB advising its shareholders that they would be better off if the company remained independent.

If talks fail again, Saint-Gobain is expected to appeal directly to the shareholders.