One of Attorney General Martha Coakley's opponents in the Democratic race for governor is calling for an independent investigation of her campaign expenses.

State Treasurer Steven Grossman suggested Thursday that the state inspector general review what he said was Coakley's ``failure to reimburse taxpayers in an appropriate and timely fashion.''

Coakley's campaign said Wednesday it was reimbursing the state nearly $11,000 in gas and mileage expenses related to her political campaigns dating back to Coakley's 2010 re-election bid.

As the state's top law enforcement official, Coakley travels in a state police vehicle, including to campaign events.

The Republican newspaper of Springfield reported Thursday that Grossman reimbursed the state for nearly $5,000 in campaign expenses during a period in which he was also assigned a security detail.