UPDATE 1-US refining sag draws attention from US Congress

(Adds comment from refiners group and Valero)

By Chris Baltimore

WASHINGTON, April 8 (Reuters) - The fact that nearly one-fifth of U.S. refining capacity now sits idle is starting to draw the attention of U.S. lawmakers, and a key House member said Congress will be looking into the refinery sag as well as record high prices for gasoline.

Oil companies are holding refinery rates at levels not seen since the 2005 hurricanes.

On paper, there are good reasons why U.S. refining capacity sits at 82.4 percent -- weak demand for gasoline and soaring inventory levels have made for low profit margins for gasoline. Instead, refiners are concentrating on churning out middle distillates such as heating oil, diesel and jet fuel, which offer better profit potential.

That explanation might not satisfy U.S. lawmakers, who are under increasing pressure from voters at home to take action on pump prices which could peak at an average $3.62 a gallon in June, according to the U.S. Energy Information Administration.

"We are looking into that, and we're looking at the questions related to why prices are so high," said Rep. John Dingell of Michigan, chairman of the House Energy and Commerce Committee, which has investigated BP Plc and Enron Corp.

The committee has not yet launched a full-blown investigation of gasoline prices or refinery capacity, but issues like refining capacity are on the panel's radar screen, Dingell told reporters on Tuesday.

A spokesman for U.S. refiners dismissed refining capacity concerns as politically motivated.