Alistair Darling is to demand £15bn in Whitehall efficiency cuts, according to the latest reports.

Ahead of Wednesday's Budget, the Times suggested the chancellor will charge the civil service with finding £10bn of efficiency savings over the three years from 2011.

That comes on top of the £5bn in reduced spending that the Treasury has said it is seeking by 2011.

Back office functions rather than frontline services are expected to be the focus of the savings.

The Times suggested that the future spending cuts will be balanced with a range of new spending commitments designed to boost the economy.

This could include £300m to improve insulation in existing and new council homes, £200m for renewable energy, tax incentives for North Sea oil companies and a 'scrappage' scheme with incentives for motorists to buy new cars.

And under-25s who have been jobless for more than a year will be guaranteed a job, work experience or training.

The chancellor said in a video message on YouTube that there had been a "huge downturn", but that the "underlying strengths" of British industry would help the country when the world emerges from recession.

"I want to make sure that we do two things. One is to help people now, through this difficult time," said Darling.

"But equally importantly we've got to prepare for the future, to invest in Britain's future to ensure that we can take advantage of the upturn, of the recovery when it comes, and it will come."