Barclays was so bent on lifting its private trading venue to the upper ranks of Wall Street dark pools that it lied to customers and masked the role of high-frequency traders, according to New York’s attorney general.

Barclays falsified marketing materials to hide how much high-frequency traders were buying and selling, according to a complaint filed by Eric Schneiderman. Barclays runs one of Wall Street’s largest dark pools, a private trading venue where investors can trade stocks mostly anonymously. Mark Lane, a spokesman for London-based Barclays, declined to comment.

Schneiderman has taken a leading role in seeking to reform how equities trade in the $23 trillion U.S. stock market, examining whether exchanges and dark pools give unfair perks to high-frequency traders. His suit against Barclays says clients such as institutional investors were the losers, led to believe they were safe from predators on a trading venue where aggressive trading strategies were in fact encouraged.

Securities and Exchange Commission chairwoman Mary Jo White on June 5 voiced concern about the level of trading on venues where bids and offers are kept private, masking the true depth of demand for shares.

Schneiderman’s action will fortify a suspicion among critics of dark pools and high-frequency firms, which proliferated in the past decade with advances in computer power and efforts to spur competition among trading venues. Namely, that in the rush to attract traders to their markets and boost profits, the venues have catered to computerized market makers to the detriment of individuals.

“Everyone who cares about the integrity of our markets should be shocked by the conduct the complaint describes,” Schneiderman said at a news conference Wednesday.

In the complaint, Schneiderman said Barclays told customers that it was protecting them from “aggressive, predatory or toxic” high-frequency traders while secretly courting them.

Barclays obscured the involvement on the dark pool of Kansas City-based Tradebot Systems, which had an “established history of trading activity that was known to Barclays as ‘toxic,’” according to the complaint. Tradebot is a high-frequency trading firm founded by its chairman, Dave Cummings, who declined to comment on the complaint.