``By mid-June, growing evidence pointed to one person, the former CEO of a large investment bank," Aguirre said in written testimony to the Senate Judiciary Committee.
Under questioning by committee members, he identified the executive as John Mack, who is the chairman and chief executive of investment house Morgan Stanley Inc.
Morgan Stanley, one of the largest US securities firms, said Aguirre had provided no evidence to support his allegation against Mack. ``No one has provided any evidence that Mr. Mack has engaged in any wrongdoing and Mr. Aguirre provided none today," a spokeswoman, Jeanmarie McFadden, said from New York.
Mack is an influential Wall Street figure and a major fundraiser for President Bush's campaigns. At the time in question, he was chief executive of Credit Suisse First Boston.
The committee is looking into problems involving the growing hedge fund industry, which commands trillions of dollars in assets and is believed to account for as much as 20 percent of all US stock trading.
In his written testimony, Aguirre said the person he called ``the suspected tipper" likely knew in advance about a merger offer, likely spoke with Pequot's CEO just before he began to trade, ``and had other personal and financial motives for tipping the hedge fund's CEO."
The allegation ``raises questions about the propriety of what the SEC has done," said Senator Arlen Specter, a Pennsylvania Republican and chairman of the judiciary panel.
Aguirre also said the SEC had told him he would risk violating the law by testifying on the matter because details of a pending investigation could be made public.
More broadly, he said, the SEC and the Justice Department are failing in their duty to protect investors in the hedge fund industry .
SEC officials deny Aguirre's allegation of political influence .
The Judiciary Committee also is examining the case of Demetrios Anifantis, a former employee of a research firm who has accused the firm of colluding with its hedge fund clients to issue biased research reports on companies.
