Opposition in France to the $10.2bn (€8bn) proposed merger between Euronext and the New York Stock Exchange is hardening after some of the most influential figures in the Paris financial markets, including heads of a banking pact with 11% of Euronext's shares, expressed concern over the deal.

Baudoin Prot, chief executive of BNP Paribas, a Euronext shareholder through the banking pact, said he did not believe the merger represented the best deal for shareholders and that he was disappointed a European solution had not been given more time for consideration.