The former chief executive of Credit Suisse First Boston John Mack said Monday he was appointed to advise in the campaign launched by Kenneth Langone, a former NYSE director, aimed at counterbidding the Big Board.

The New York Stock Exchange and Archipelago $4.7 billion (£2.5 billion) merger appeared to be the obstacle for some people in their attempts to grab power over the NYSE that faces tough times since the scandals with its executives.

Billionaire Langone who is the target for the New York State Attorney General Eliot Spitzer is in the process of launching a campaign that could help the rival group to derail the merger between the NYSE and the electronic trading firm.

On Monday, the group held a meeting on which it appointed Mr. Mack a spokesman and senior adviser to the counterbidding campaign, according to the people familiar with the matter.

The campaign is mounted both by Mr. Langone and his strategic partner Stanley Druckenmiller, the former Soros strategist.

"The firms want to understand the value proposed and if there is a case that this deal is undervalued," said Mr. Mack.

Under the terms of the deal between the NYSE and Archipelago, Archipelago’s shareholders will receive 30% of the combined company.