Lewis said, “I spoke to dozens of investors, big investors, famous investors who said that, ‘When Brad Katsuyama came into my office and laid out to me how the market was rigged, my jaw hit the floor. I mean, I knew something was wrong. I just didn’t know what it was and no one had told us.’”

Eric Ryan, a spokesman for the New York Stock Exchange, and Nasdaq OMX Group Inc.’s Rob Madden declined to comment on Lewis.

“We completely disagree with allegations that the U.S. equity market is rigged,” Bats President Bill O’Brien said in an e-mail. “While we should never stop trying to improve our market structure, it is unfair and irresponsible to accuse people simply because they use technology and enhance competition. This has helped make our market the most competitive and liquid in the world, greatly benefiting individual investors.”

New York

New York’s Schneiderman is examining the sale of products and services that offer faster access to data and richer information on trades than is normally available to the public. Wall Street banks and rapid-fire trading firms pay for these services, providing millions of dollars in quarterly sales to exchanges and helping ensure their markets are supplied with standing orders to buy and sell stocks.

Bloomberg LP, the parent of Bloomberg News, provides its clients with access to some proprietary exchange feeds.

The investigation threatens to disrupt a model that market regulators have permitted for years as high-speed trading and concerns about its influence have grown. Trading firms pay to place their systems in the same data centers as the exchanges, a practice known as co-location that lets them directly plug in their companies’ servers and shave millionths of a second off transactions.

High-frequency-trader Virtu publicly released its initial public offering filing in March. The New York-based market maker, which provides quotes in more than 10,000 securities and contracts on more than 210 venues in 30 countries, said it had turned a profit every day except one for five years. The company uses IEX.

CFTC Review

Virtu disclosed in the IPO filing that the U.S. Commodity Futures Trading Commission is looking into its trading from July 2011 to November 2013, examining its “participation in certain incentive programs offered by exchanges or venues,” according to the IPO filing. Virtu said it doesn’t believe it broke any laws or CFTC rules.