Shopping on the internet may not be as environmentally friendly as is often claimed, according to new figures showing that the boom in home deliveries has resulted in a rise in overall emissions from vehicles.

All the savings in carbon dioxide emissions since 1997 from the introduction of more efficient cars have been outweighed by the growth in emissions from vans and lorries.

The total CO2 emitted by cars fell by 2.3 million tonnes, or 3.2 per cent, between 1997 and 2005. Over the same period, emissions from vans rose by 3.3 million tonnes, or 24.4 per cent, and from lorries by 2.6 million tonnes, or 10 per cent, according to a report by the Society of Motor Manufacturers and Traders.

Online retailers claim that it is more efficient for one van to deliver to several addresses than for each household to travel by car to the shops.

British households spend more than £3billion a month on internet goods and in April online spending rose by 55 per cent compared with the same month last year. But the SMMT said home deliveries were often poorly organised, with vans returning long distances to depots after making only one or two stops. People were also buying many more goods and services and employing tradesmen from further afield than a local company.

The number of vans on the road has increased by almost a third, or more than 730,000, in the past decade. The total distance travelled by vans is growing four times faster than the distance travelled by cars. Cars are subject to industry-wide targets for reducing carbon dioxide emissions and dealers have to display colour-coded labels in their showrooms indicating the environmental efficiency of the models on sale. There are no such targets or labelling systems for vans. The SMMT report said that the average new car sold last year emitted 167.2g of CO2per kilometre (g/km), down 11.9 per cent since 1997. It said the equivalent figures for vans were not collected.

An SMMT spokesman said: “We do not believe vans are getting dirtier but there are many more of them and they are travelling much further. We used to employ a plumber or electrician from our home town but now they may come from the other side of the region.

“There is also very poor planning of distribution by some retailers, who may make only one delivery before returning to the depot.”

Transport 2000, the sustainable transport campaign, said people who believed they were helping to save the planet by shopping online needed to consider how far their goods travelled.

In the past 20 years, the major retailers have saved money by closing hundreds of depots. They now organise deliveries from a handful of giant distribution centres, meaning vans have to travel much further to deliver goods to shops or homes.

Stephen Joseph, the campaign’s director, said: “There has been a great debate about emissions from aircraft and cars but some of the biggest increases have come from vans and lorries. We need specific targets for cutting CO2 from freight.”

The European Commission has proposed that, by 2012, the average new van sold in Europe should emit 175g/ km and the average new car 120g/km.

The RAC Foundation said a labelling system for vans showing their CO2 emissions would help customers choose retailers with more efficient fleets.

Edmund King, the foundation’s director, said: “People have no way of measuring one company against another. With a labelling system, discerning consumers could put pressure on companies to invest in the cleanest vans.”

Mr King said online retailing did not necessarily replace car journeys because 80 per cent of people liked to view goods in shops before ordering them. They might also receive multiple deliveries from different internet retailers when previously they had made a single trip to a shopping centre.

He said retailers and haulage companies should consider changing their policy of sending out goods only a short time before they were needed. “It used to be that a single lorry a week would deliver all the goods required but now there may be several trips as things run out.”

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