A boardroom split has opened up at Sanofi-Aventis, France’s largest drug company, over a proposed $54 billion (£25 billion) deal to acquire Bristol-Myers Squibb (BMS), of the US, that would create one of the world’s largest pharmaceuticals groups.

The Times has learnt that a disagreement over strategy has emerged between Jean-François Dehecq, the Sanofi chairman, who favours a transformational deal with BMS, and Gérard Le Fur, his younger chief executive, who has emphasised the need to focus on the group’s internal drug research and development programme.

Banking sources assert that there is a “significant difference” in tactics between the men, which has led to friction over the direction of the group.

“It’s a question of ego rather than the timing of any deal,” said one, who added that, ultimately, Mr Dehecq’s view is more likely to prevail because he wields greater authority in the Sanofi boardroom and among big shareholders, including the oil group Total and the cosmetics company L’Oréal.

Mr Dehecq, a Sanofi veteran, has been the driving force behind the company and has overseen hundreds of acquisitions since its creation in 1973.

He has also made little secret of his desire to create a world-beating pharmaceuticals group.

Last month Sanofi shelved preliminary talks over a deal with BMS because of concerns over valuations and a legal wrangle surrounding the companies’ top-selling drug, the blood-thinner Plavix, on which they collaborate.

No substantive discussions are thought to have been held since but there is mounting speculation that, assuming Mr Dehecq’s views triumph, Sanofi may seek to dust off its merger plans after the outstanding litigation over Plavix has been settled.

Plavix was the world’s second-bestselling medicine in 2005 with sales of $5.9 billion.

The lawsuit revolves around a patent deal struck with Apotex, a Canadian drug maker, last summer, which later allowed it legally to flood the American market — easily the world’s largest — with a low-cost generic version of the medicine.

The move triggered a 62 per cent slide in sales of branded Plavix, and Peter Dolan, the BMS chief executive, resigned in September for his role in the debacle.

Yesterday a spokesman for BMS said that the closing written legal arguments had been submitted and that a judge was reviewing the evidence. A final judgment is possible by the end of next month.

Julien Dormois, pharmaceuticals analyst at Bryan Garnier, the Paris investment firm, said: “I am quite convinced that an offer will be made.”

BMS declined to comment on a possible merger, while Sanofi denied that there was any difference in strategy between its chairman and chief executive.

A successful merger between Sanofi and BMS would create a pharmaceuticals company with combined sales of $56 billion, roughly the same as Pfizer, the world No 1.

Their combined market capitalisation would be about $172 billion. Pfizer’s market capitalisation is $182 billion.

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