Supermarkets give out enough plastic bags every year to cover an area bigger than Sussex and Surrey put together, an investigation has revealed.

Lewes MP Norman Baker discovered an estimated 17.5 billion bags were handed to customers each year.

Supermarket lorries travel 670 million miles per year - the equivalent of two return trips to the moon every day.

Mr Baker, the Liberal Democrats' environment spokesman, is calling for action by the Government and supermarket chains to cut the use of bags and increase recycling.

His research found only 26 per cent of the cost of food products accounted for the food itself.

The rest of the cost comes from packaging, transport, advertising and the supermarkets' mark-ups and overheads.

The Liberal Democrats' report How Green Is Your Supermarket also found:

There is now one supermarket per 10,000 people in Britain
Stores belonging to the big nine chains cover an area equivalent to 15,000 football pitches
Customers spend up to £15 billion on food packaging every year.

Mr Baker gathered information from Asda, the Co-op, Marks & Spencer, Morrisons, Safeway, Sainsbury's, Somerfield, Tesco and Waitrose to produce the report.

He said each firm had some green policies but there would be significant improvements if all adopted better practice.

He said: "Today customers are asking more from their supermarkets than 'pile 'em high and sell 'em cheap'.

"They want to know these companies are taking a responsible attitude towards the environment.

"The Government must take action to encourage supermarkets to establish national standards and reach national targets."

He called for supermarkets to have "Bags For Life" on display at check-outs, "Please Re-Use" messages on every bag, cash incentives and recycling points.

A tax on plastic shopping bags was credited with helping reduce their use by 90 per cent in Ireland.

The report also found only about seven per cent of food sold by the big supermarkets was organic, slightly more than half of which comes from British producers.

Supermarkets make between one and two per cent of turnover from food produced within a 30-mile radius, although some have regional buying policies for a few products.

The British Retail Consortium, which represents the major chains, said plastic bags accounted for less than one per cent of litter.

It said many bags were biodegradable, most supermarkets had "Bag for Life" schemes and a tax on bags would hinder steps to manufacture them from recycled plastic.