Kentucky Attorney General Jack Conway has sued Marathon Petroleum Co. accusing the company of anti-competitive practices leading to higher gas prices in the state.
Conway said Tuesday that Marathon's monopoly on wholesale gas supplies has been allowed "to run rampant" in Kentucky.
The company did not immediately reply to emails seeking comment.
Conway is the front-runner in the state's Democratic primary for governor next week. Conway says the federal lawsuit isn't politically timed, saying he has a duty to act when consumers are being treated unfairly at the pumps.
The suit continues an adversarial relationship between Conway and Marathon. Conway started investigating gas prices early in his first term in 2008.
The suit, among other things, seeks to end supply agreements that Conway says prevent competition.