Gordon Brown has vowed to free Britain from the "dictatorship of oil" by investing in nuclear and renewable energy.

In a keynote speech to the Scottish CBI in Glasgow, the Prime Minister promised the Government will do all it can to help families and businesses to pull through the global economic downturn.

After Chancellor Alistair Darling's bleak assessment of the current economic conditions as the worst for 60 years, Mr Brown insisted he is "cautiously optimistic" about Britain's ability to ride out the storm.

But he faced a renewed attack on his leadership from former home secretary Charles Clarke, who said Mr Brown should "stand down with honour" unless he is able to turn around the fortunes of the Labour Party within months.

Mr Brown said: "Undoubtedly we face a challenging period in the British economy - particularly given our position at the heart of the world's financial markets - and both the Chancellor and I understand the difficulties you face.

"But while never complacent about our economic prospects, I am also cautiously optimistic about the long-term resilience and underlying strengths of the British economy."

He promised further "targeted support" for families struggling with rising food and energy bills.

Mr Brown said that Britain stands to gain as the world economy doubles in size once the current turmoil is over.

But he said the extreme volatility in world oil prices underlined the need for a "revolution" in the way the country used energy resources, reducing its long-term dependence on oil.

"So today I set a new ambition to free Britain from the dictatorship of oil," the Prime Minister added.

He announced the approval of a new offshore wind farm near Walney Island and a major pilot programme for electric cars.

And he held out the prospect of at least one million new jobs being created in the new "green economy" by 2030 if British companies were prepared to invest in low-carbon technologies.

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