Massachusetts Secretary of the Commonwealth William Galvin is investigating broker/dealers routing orders to exchanges that offer rebates.

Galvin in a press release said he is focusing on whether the practice creates a conflict of interest leading to the broker/dealers failing to meet their best execution obligations. In line with the probe, his office sent letters to Charles Schwab & Co. Inc., Scottrade Inc., TD Ameritrade Inc., Fidelity Brokerage Services LLC, E*TRADE Securities LLC, Edward D. Jones & Co. LP and Morgan Stanley & Co. LLC.

"If financial rebates or kickbacks create a conflict that results in less than the best deal for the investors, this practice must stop," Galvin said.