WASHINGTON -- Sen. Bob Casey yesterday called for a hefty new tax on oil company profits to fund a program intended to help low-income families pay their transportation costs.

The Pennsylvania Democrat also said he would try to repeal several tax subsidies for oil companies. That money, he said, would help finance research into alternative fuel sources.

Joined by his fellow freshman Democratic senators, Mr. Casey struck a loud populist note, criticizing President Bush's handling of energy issues and accusing the administration of forging close ties with the oil industry while doing little to help consumers who face rising gas prices.

"Here's what you hear from the Bush-Cheney Big Oil conglomerate: They say you have it wrong; everything is wonderful --we have to continue the tax breaks for millionaires," Mr. Casey said. "And if you happen to be a billionaire who owns an oil company, you get another break. You get Big Oil tax credits and subsidies."

At the start of the week, the average price for a gallon of gasoline in the United States was $2.91, according to the federal Energy Information Administration. That's up from $1.45 in January 2001, the start of the Bush presidency. Mr. Casey said gas prices in Pennsylvania have risen by 20 cents per gallon in the last month.

His proposed tax, part of legislation he planned to introduce in the Senate, would kick in when oil prices top $50 per barrel. At that point, the government would tax 50 percent of an oil company's profits. As of April 20, the average world price for a barrel of oil was about $63.

The new tax revenue would fund a program that the senator likened to LIHEAP, the Low Income Home Energy Assistance Program. The federal government would give money to states, which would then distribute money to low-income families to help them cover their gasoline bills. The program would set a cap of $1,500 per individual and $2,500 per family.

Mr. Casey said oil companies need to start "paying their share" of the burden of high energy costs. He noted that ExxonMobil, the world's largest energy company, has earned more than $9 billion in profits, according to its latest quarterly report.

But John Felmy, chief economist for the American Petroleum Institute, called the senator's plan a "disappointing, uninformed attack on the oil industry." He argued that ExxonMobil's actual profits were lower -- about 9.2 cents per dollar -- because of the industry's considerable investments in expanding production capacity and other areas.

"While we have huge revenues, we have huge costs," Mr. Felmy said.

White House spokesman Alex Conant said the president already has called upon Congress to quickly pass energy legislation that would promote development of more alternative fuels and efficient cars, helping reduce gasoline consumption by 20 percent over the next 10 years. "The best way to reduce our addiction to oil is by embracing new technologies and alternative fuels, not raising taxes," he said.

Mr. Casey's bill also aims to create a National Energy Security Research and Investment Reserve, which would support research on biofuels such as ethanol. He hopes to get the money by repealing some oil company subsides authorized by the Energy Policy Act of 2005.

Mr. Felmy asserted that the industry actually lost money under that legislation.

Mr. Casey was joined by six freshman Democrats and one Independent, Bernie Sanders of Vermont, in announcing his bill. He acknowledged that Congress has been unable to pass similar oil taxes in recent years, but he said the Democratic victory in last year's election has created fresh momentum.