ONE of the biggest shareholders in the New York Stock Exchange last night came out in opposition to a merger between the Big Board and Euronext, the operator of five European markets, as talks between the two exchanges continued.

Thomas Caldwell, the head of Caldwell Financial, 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.”

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.

Bob Greifeld, Nasdaq’s chief executive, has walked away from one bid for the LSE and is not allowed to bid again until the autumn. He can take his holding up to 29.9 per cent in purchases in the market, but few analysts expect him to go much higher than 25 per cent, a blocking stake that would shut out other bidders.

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.”

The investor was formerly head of one of the largest groups of NYSE members and still represents a large number of smaller shareholders. He also claims to be talking with several institutional shareholders who between them own a significant percentage of the NYSE shares.

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