Opposition to the €16bn ($21bn) merger between Euronext and the New York Stock Exchange is hardening with French and Dutch companies and shareholders condemning the deal.

In the latest attack, the Dutch association of listed companies, which represents businesses quoted on the European exchange, said it had two serious concerns. Martin Noordzy, the association's adviser, said: "The first is we fear US rules and litigation practices will arrive in the Netherlands. We are not convinced by Euronext's assurance the creation of a special US foundation will mean the merger can be broken up in the event of ‘rule creep'. "Who is going to question this merger a couple of years down the line? US lawyers tell us the Securities and Exchange Commission would never allow such an agreement." The second fear is a monopoly of exchanges. Noordzy said: "Once you are listed on the NYSE, it is difficult to relist anywhere else. This American restriction is being exported to Europe, particularly if Nasdaq buys the London Stock Exchange." Noordzy added the association was urging Euronext shareholders to consider the social as well as financial merits of the offer. He said: "We will be lobbying Gerrit Zalm, the Dutch finance minister, because he has to approve this merger." Dutch Euronext shareholders will publish a report on the merger on Thursday. It is expected to back concerns regarding US regulatory interference. The report will come from Eumedion, the Dutch corporate governance lobby group that includes ABP, the €190bn pension scheme for Dutch civil servants, and a Euronext shareholder as a member. ABP has raised concerns about European corporate governance rules being dominated by US Sarbanes-Oxley legislation. Rients Abma, director of Eumedion, said: "We were sceptical about the merger for this reason and our report will probably reflect this." Several chief executives of France's CAC 40 companies are believed to be supporting Henri Lachmann, chairman of Schneider Electric, who last week slammed the deal as a US takeover. A French banker said: "I have had four chief executives from CAC 40 companies on the phone saying they are 100% behind Henri Lachmann. I don't believe this game is finished yet. Many believe it is only a matter of time before the London Stock Exchange asks Euronext to step in to make a white-knight bid against Nasdaq." Lachmann compiled a report for Paris Europlace, the lobby group of banks and investors that make up a large part of Euronext's users and shareholders. It criticised the merger's terms and proposed an alternative deal with Deutsche Börse. Last week, he mauled the remaining deal after the Germans pulled out: "We have got to put away the pens on this. Nothing is forcing Euronext to jump into the arms of the NYSE. The project being presented is a lie – it is not a merger of equals but a takeover by the NYSE. We have to re-explore the potential for an exchange merger in Europe." Euronext shareholders will meet on December 19 in Amsterdam to vote on the merger. Regulatory approval for the deal is expected to be granted this week.