SANTA FE -- New Mexico Attorney General Gary King is asking the gasoline industry why his state's retail prices continue to head the national average.

He could try reading last year's newspapers instead.

King announced yesterday that he had demanded answers from all participants in New Mexico's retail gas and diesel supply chain. The release said King is reacting to legislative and consumer concerns about the issue.

The New Mexico legislature earlier this year passed House Joint Memorial 42 authorizing King to investigate price disparities between retail gasoline and diesel in the state over the past 12 months. HJM42 says diesel prices have fallen less than gasoline, hurting the state's economy.

The attorney general wrote a letter dated June 25 to participants in the industry asking why New Mexico now has the highest average retail gas prices in continental U.S. Three months ago, the letter notes, prices were below the national average.

"Even with decreasing prices at the pump, New Mexicans are experiencing significant increase relative to other Americans," King's letter stated. It was sent to suppliers, distributors and retailers of gasoline and diesel.

But a report last spring by corporate-supported Citizens Alliance for Responsible Energy (CARE) explained why New Mexico's gasoline was then the Southwest's most expensive. The report was distributed statewide by the AP.

New Mexico's many smaller, outlying towns drive up the average retail gas price because of higher transport costs, CARE Founder and Senior Advisor Mark Mathis explained. Trucking gasoline 200 miles in a tanker adds around 10 cents to a gallon of gas at the pump, he said.

Adding to the problem, the report pointed out, is a pipeline network that's less comprehensive than neighboring states. New Mexico imports 7,000 barrels of oil daily despite a booming statewide energy sector, Mathis added.

King asked the recipients of his letter to respond to five specific questions about retail gasoline and diesel prices by July 25.