The New York Stock Exchange has hired a senior Citigroup lawyer to monitor specialist market-makers. It is one of a series of appointments aimed at convincing the Securities and Exchange Commission, the US regulator, that the exchange has toughened its stance on regulation.

John Malitzis, formerly an associate general counsel within Citigroup's institutional equities division, will join the exchange as vice president for specialist surveillance. He will replace Dan Saporito, who has spent more than three decades with the exchange.