Tesco is to run threequarters of its distribution fleet on biodiesel from next month.

The supermarket giant estimated that by using the B50 blend - 50 per cent ordinary diesel mixed with biofuel - it would cut its greenhouse gas emissions by more than 70,000 tonnes a year, equivalent to filling 15,000 swimming pools or 400 Royal Albert Halls.

It said it had already ensured biofuel blends were stocked on its petrol forecourts, resulting in the reduction of a similar level of carbon dioxide emissions to the distribution initiative.

The retailer has 2,000 lorries responsible for transporting goods to 754 stores and 716 smaller Express outlets.

Chief executive Sir Terry Leahy denied Tesco was responding to external pressure to improve its public image and told The Sunday Times: " My aim has always been to be number one in the eyes of customers, not in anyone else's eyes. This issue is growing in importance for customers and we have got to respond."