Last night it emerged that Thomas Caldwell, head of Caldwell Financial, one of the biggest shareholders in the New York Stock Exchange, is against any tie-up with the pan-European exchange, Euronext.

As talks continue, Caldwell said: “The NYSE is the jewel in the crown of world exchanges and Euronext comes nowhere near it. I and others like me do not want to see the NYSE diluted by a deal with Euronext.”

London Times Business reports: “John Thain and Jean-François Théodore, the chief executives of the NYSE and Euronext, have been in talks to discuss a possible merger. There was speculation that the NYSE had lost interest in the London Stock Exchange after its rival Nasdaq acquired a 24.1 per cent stake in the LSE.”

In another neck of the woods, Nasdaq’s chief executive, Bob Greifeld, who recently walked away from one bid for the London Stock Exchange, is barred from bidding again until the autumn. However, he can take his holding up to 29.9pc, but few expect him to exceed 25pc, a blocking stake designed to shut down other bids.

Euronext’s market capitalisation is about $10 billion (£5.3 million), close to NYSE’s $11 billion and a comparison that has prompted some analysts to suggest that they are equals. However, Mr Caldwell said: “These four or five small exchanges do not add up to an institution like the NYSE, they are simply worlds apart.”