If the SEC fails to ban the practice, Schumer said he would introduce legislation in the Senate to prohibit flash trading.

Schumer added that he welcomed Schapiro's decision. "The agency is absolutely making the right call by stepping up and ending this unfair practice," Schumer said in a .

Flash orders are offered by a number of stock exchanges, including the Nasdaq, Jersey City-based DirectEdge and BATS Exchanges Inc. of Kansas City. For a fee, these exchanges flash, or make available, information about buy and sell orders a few milliseconds before the one-second limit by which that the information is supposed to become publicly available under current SEC Regulation National Market System regulations.

In his letter to Schapiro, Schumer said the practice is believed responsible for increasing the volatility on U.S. stock exchanges and in 2008 accounted for $21 billion in profits to those taking advantage of it.