New York’s attorney general has called for curbs on services provided to high-frequency traders.
In particular Eric Schneiderman highlighted services that allow traders to get faster access to information.
He said traders can make “rapid and often risk-free trades before the rest of the market can react”.
High frequency trading is where firms create sophisticated computer programs to buy and sell stocks in milliseconds, faster than any human.
It has grown in popularity in recent years, but it has also come under scrutiny.
“Rather than curbing the worst threats posed by high-frequency traders, our markets are becoming too focused on catering to them,” said Mr Schneiderman.