T. Boone Pickens' conversion from Texas oilman to darling of the US renewable energy industry continued apace this week with the billionaire investor testifying to a Senate committee that oil prices could hit $300 (£150) a barrel if the country does not step up efforts to limit its dependence on foreign oil.

Pickens made his debut on Capitol Hill to promote his self-styled "Pickens Plan" for enhancing US energy security by generating up to 22 per cent of the country's energy from wind turbines over the next decade.

He told a Senate committee that the US already imports nearly 70 per cent of its oil and that this would rise to 80 per cent over the next 10 years if it does not increase investment in renewable energy and natural gas. "If we continue to drift, oil will hit $300 a barrel in 10 years," he warned, adding that legislators needed to show greater leadership to encourage people to curb energy use.

"The American people have not been asked to do what needs to be done," he said. "I'm going to awaken the American people and they will see what they're up against. When they walk out of the room, they're going to turn off the lights. . . . We're going to become much more sensitive to energy in the country, and that's good."

Pickens said that he was not against an expansion in offshore oil drilling, a central plank of the Bush administration's strategy for limiting dependence on imports, but warned that there were simply not sufficient US oil reserves to meet rising demand. He argued instead that there needed to be a much greater focus on bolstering wind energy capacity.

Earlier this month, 80-year old Pickens announced he was to spend $58m (£29m) on a PR campaign to promote the "Pickens Plan", which calls on the government to invest up to a trillion dollars to replace natural gas with wind energy and then use the excess natural gas to power vehicles.

Pickens himself has long maintained that far from converting into an environmentalist, he sees the strategy as a great opportunity to make money. His BP Capital hedge fund has invested heavily in the natural gas sector, while he also recently announced plans for a massive £12bn wind farm in his home state of Texas.