LOS ANGELES, Calif. -

Sen. Dianne Feinstein has called for a federal investigation into gas prices in California because she doesn't think they are related to supply and demand.

Californians are paying an average of $4.668 a gallon, the highest price in the nation. Many motorists are paying over $5.

Feinstein says that paying hundreds of dollars every time you fill your tank is unthinkable. For the second time in the last few months, the California Democrat has sent a letter to the Federal Trade Commission asking for an immediate probe.

She also asked in August when gas was 45 cents cheaper.

Elizabeth Emken, Republican challenger for U.S. Senate in California against Feinstein, said Monday her Democratic rival was simply calling for another useless government investigation.

"If Dianne Feinstein wants real answers, she should look in the mirror, said Emken.  "Today's high prices are the logical consequence of her 'none of the above' strategy. It's common sense to ordinary Americans that restrictions on domestic energy, excessive taxes, and oppressive regulations would lead to high gas prices."

Emken said, ""My 'all of the above' approach to energy independence would encourage innovation and investment and use the resources at America's disposal so that we are never again at the mercy of outside influences."

Gov. Jerry Brown over the weekend ordered state smog regulators to allow winter-blend gas to be sold three weeks early in the state.

Experts are predicting prices will climb to $4.85 before coming down.