Upbeat: Gordon Brown is cautiously optimistic about Britain's chances of a swift economic recovery

Gordon Brown held out the hope of economic recovery last night as he voiced 'cautious optimism' about Britain's prospects.

His prediction of a short-lived downturn was designed to dispel the damage done by Alistair Darling's gloomy warnings of hard times ahead just days ago.

But it promptly sparked Tory claims that the Prime Minister is at odds with the Chancellor and is glossing over the extent of the difficulties facing the economy.

And it confirmed that the Government has given up hopes of persuading the major energy companies to consider offering low-income customers a rebate on their fuel bills.

Mr Brown used a keynote speech to the CBI in Scotland to flesh out what has been a week devoted to his economic relaunch.

He vowed to wean Britain away from the 'dictatorship of oil' by favouring nuclear and renewable energies.

And he issued a message of defiance against the Scottish National Party by promising to defend the Union at all costs.

But it was his upbeat talk on the economy that was designed to show Mr Brown is focused on the needs of families struggling to cope with climbing food, fuel and housing costs.

Mr Brown tried to repair the damage done by Mr Darling's remarks in a weekend newspaper interview which helped to send the pound plummeting on the foreign exchanges.

The Chancellor caused consternation in Downing Street by suggesting the current economic conditions faced by Britain as the worst for 60 years.

But 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, with the Government's much-trumpeted package for tackling fuel poverty due to be published at the end of next week.

While people understood that no national government alone could 'put everything right that is creating hardship', he said that they did look to ministers to take action to help them through difficult times.

'We will not let them down,' he said. 'We will do what it takes to bring security to families on modest and middle incomes. And we will ensure that no-one who is prepared to work hard and adapt to change will lose out as a result of global forces.'

Once the current turmoil was over, Mr Brown said that Britain stood to gain as the world economy doubled in size over the coming years.

At the same time, however, 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,' he said.

He announced the approval of a new offshore wind farm near Walney Island, off the coast of Barrow-in-Furness, with 139 turbines making it one of the largest in the UK.

Mr Brown attacked the SNP, warning: 'Set against the global challenges facing us today, the bleak separatist obsession of the nationalists to split Scotland from the rest of the UK looks at best like self-indulgent posturing. At worst like a wilful denial of the realities of the world we live in.'

Shadow Chancellor George Osborne accused Mr Brown of being in denial about his leadership and the economic crisis.

'Gordon Brown says he is cautiously optimistic, while Alistair Darling says the UK’s economic problems will be more profound and longer lasting than people expected,' he said.

'We have a Labour government descending into civil war and a Chancellor and a Prime Minister who publicly disagree on the severity of the problems we face.'