John Mack, the former chief executive of Credit Suisse First Boston who now works for private equity group Kohlberg Kravis Roberts, has been drafted in by a potential rival bidder for the New York Stock Exchange.

Mack, who last September joined the board of KKR Financial Corporation, the private group's real estate arm as a non-executive, yesterday met a group of 10 Wall Street executives to discuss the merits of the NYSE's $4.7bn (€3.6bn) agreed merger with Archipelago, the electronic exchange.