Major retailers have signed up to a government initiative to cut the use of plastic bags in half by spring 2009.

At the moment the agreement is only with supermarkets including Asda, the CO-OP, Marks and Spencer, Sainsbury's, Somerfield, Tesco and Waitrose have all signed the pledge which was thrashed out with the British Retail Consortium (BRC).

However, the BRC has hinted it could be extended in the future by saying it will be underpinned by 'action across retail sectors'.

The agreement to reduce the volume of carrier bags provided to customers by 50% - against 2006 levels, covers England, Wales and Northern Ireland.

The number of bags saved by spring next year through this agreement would fill 60 Olympic-sized swimming pools, or fill the Royal Albert Hall one and a half times.

Stephen Robertson, BRC Director General, said: "This new partnership with the Government, underpinned by action across the retail sector, offers exciting new opportunities to help our customers across the UK to do the right thing.

It's one more step towards reducing waste and environmental impact."

DEFRA and WRAP (the Waste & Resources Action Programme) set retailers the target of reducing consumer carrier bag usage by 25% by the end of 2008.

A target which B&Q has exceeded by 57%, equating to about 24.5m individual bags saved.

In the UK 12.4 billion bags are given away every year but a carrier bag only has a useful life of 20 minutes before it is dumped.

B&Q UK has been running a trial charging customers in Scotland 5p per carrier bag since 2004 and customers in the North East have been charged 5p since 2005.

Since the trials were introduced the retailer has donated over £50,000 to Keep Britain Tidy and Keep Scotland Beautiful campaigns.

Euan Sutherland, CEO, B&Q and Kingfisher UK Division said: "B&Q has a long history of sustainability and we've invested time in developing the right chargeable carrier bags for our customers.

Plastic bags can cause real community and environmental problems as they significantly contribute towards litter problems and can also harm wildlife.

"At B&Q we have always believed that lots of small changes add up to a big difference and through our range of bag options we are urging customers to re-use bags wherever possible.

"We're delighted to be helping the environment by reducing the volume of plastic bags."