SACRAMENTO (CBSLA.com) — State lawmakers in Sacramento were set to hear testimony Tuesday on whether drivers in Southern California and statewide were gouged by oil companies during a dramatic spike in gas prices earlier this year.

Jamie Court, who heads advocacy group Consumer Watchdog, will be among those called to testify before the joint hearing of the California Senate Transportation and Housing, Energy, Utilities and Communications Committee.

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Court is expected to present the findings of a new report entitled “Price Spiked: How Oil Refiners Gouge Californians On Their Gasoline and What It Costs”, which claims Californians paid $550 million extra for their gasoline in February, when prices soared to among the highest in the nation.

The report also found that California oil refiners have about half as much gasoline on hand than the rest of America, which can fuel a “volatile market that leads to gasoline price spikes.”

A review conducted by Consumer Watchdog of 10 years of data collected by the federal and state government found California gasoline prices have averaged 32 cents more per gallon than the national average for gasoline prices over the last decade, about $3.30 in California vs. $2.98 in the rest of the nation.

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Refinery consolidation and emergency supplies were among two major factors cited in the report.

While the rest of America averaged 18 days of gasoline supply in refineries and bulk terminals, California refiners only kept just under 11 days of gasoline supply on hand – about 48 percent less – which in turn left the system vulnerable to price spikes, according to Court.

“The way they do it is by keeping California running on a week’s less gas than the rest of the nation,” Court told KNX 1070 NEWSRADIO. “By doing that, they ensure themselves profits.”

To remedy the situation, the report recommended new state legislation to require refiners to keep another week’s worth gasoline supplies on hand so that it matches national days of supply.

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The report also calls on California to accelerate the transition to electric vehicles and other alternative transportation technologies.