The owner of the Jewson building materials chain has launched its campaign to swing shareholders behind its £3.62 billion bid for plasterboard giant BPB.
Bosses at BPB immediately said the company would write to shareholders to urge them to kick the proposal into touch.
French company Saint-Gobain carried out its promise to go direct to investors after previously failing to win the support of the UK company's board. Saint-Gobain, which has 40 businesses and 18,500 staff in the UK and Ireland, posted its offer of 720p a share in a document to shareholders yesterday.
The move was met with the same response from BPB's board, which said it had "no hesitation" in recommending that its shareholders reject "this unwelcome offer" which it believed substantially undervalued the company.
BPB said it would write to shareholders within 14 days to explain its rejection of the offer, adding that it "strongly urged" shareholders to take no action in respect of Saint-Gobain's offer.
BPB runs 90 factories worldwide and sells products such as insulation and ceiling tiles in more than 50 countries. The company's UK operations include British Gypsum Isover, a wall and ceiling plaster joint venture with Saint-Gobain. The French company acquired ownership of Jewson and fellow builders merchant Graham in a £1.04 billion deal with Meyer International in 2000.
Jewson operates more than 440 branches nationwide.
Saint-Gobain told shareholders its takeover price represented a 40 per cent premium to BPB's share price ahead of the offer period.
Jean-Louis Beffa, chairman and chief executive, said: "We believe that BPB will benefit from being part of the Saint-Gobain group. The business rationale for combining the two businesses from a product and geographic perspective is compelling."