But Darling also expected to announce £500m package to boost green housing and energy initiatives

Alistair Darling will demand public spending cuts of £15bn in this week's Budget but is due to announce a major investment drive into green technology, according to reports.

The chancellor is widely expected to reduce the rate of growth in annual spending in Wednesday's announcement, as concerns over the nation's debt soar. He has already said he is looking for £5bn efficiency savings by 2011 and is expected to say this week that the figure should be increased by £10bn over the following three years.

It is not yet clear where the proposed cash savings will be made or if spending on construction or infrastructure will be affected. It is thought that much of the efficiency could come from cutting back public sector office staff.

But Darling is also thought to be preparing to announce a £500m green stimulus package, which will include £300m towards insulation of existing homes and new public housing and £200m to boost the growth of the UK wind energy and hydroelectric power and other renewable industries.

Alistair Darling
Darling: "invest in Britain's future to ensure that we can take advantage of the upturn"

It is also through the government will unveil plans to dramatically accelerate the race to build carbon capture and storage plants, where harmful gases are caught, processed and stored underground.

In an online message to the nation on YouTube, Darling said: “I want to make sure that we do two things. One is to help people now, through this difficult time. 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.”