Families willing to exchange their petrol or diesel car for one that plugs into the mains are being sought to take part in a Government trial of electric vehicles.

They will have to be prepared to run the risk that the car's battery will run flat during a journey and then take several hours to recharge.

In return, they will enjoy running costs of about 2p a mile, discounts on congestion charges and the satisfaction of knowing that their electric cars will be emitting less than half the carbon dioxide of even the most efficient internal combustion engine.

Lessons from the trial, which will start next year and involve up to 100 electric cars in cities across the country, will inform the Government's strategy for accelerating the take-up of electric vehicles.

Speaking to The Times, Geoff Hoon, the transport secretary, said electric cars would appeal most to two-car families who used the second vehicle primarily for short journeys around town.

Even the most advanced electric cars currently being developed have a range of less than 40 miles before they need recharging.

Mr Hoon, who owns a Mini and a Ford Galaxy people carrier, said: "A lot of people have a car for long-distance travelling and a small runabout for taking the kids to school. We need to find out whether electric cars are practical."

"They are not going to be racing up and down the M1 but they are going to be used more around cities," he said.

"We also need to consider how people in tower blocks can recharge their cars. It's not so easy when you don't have a driveway."

Mr Hoon said the London congestion charge exemption for hybrid cars had been very effective in encouraging take-up and he hinted that drivers could be given further incentives to switch to electric vehicles.

The cars used in the trial are likely to be a combination of pure electric vehicles, which are powered only by their batteries, and plug-in hybrids which have a petrol engine that starts up when the battery runs low.

A study by Arup, commissioned by the Department for Transport, found that the number of electric cars in Britain could rise from 2,000 at present to more than 1.5 million by 2020 if the Government acted decisively to stimulate demand. To achieve that, it would need to ensure that by 2015, drivers had easy access to recharging points and that the whole life cost of owning an electric car was comparable with conventional cars.

Arup calculated that, if the major manufacturers committed themselves to mass production of electric cars rather than the small-scale trials seen so far, almost half Britain's cars could be running without fossil fuels by 2030.

Manufacturers were yesterday invited to submit bids by January to participate in the £10 million trial. They must submit plans for recruiting volunteers and lend them cars which emit 50g of carbon dioxide per kilometre or less, half the emissions of a Toyota Prius hybrid.

The trial will be part of a £100 million five-year programme to stimulate the design, manufacture and purchase of electric vehicles.

In a second trial costing £20 million, more than 150 electric vans will be tested by local authorities in Liverpool, Newcastle and Gateshead, Coventry, Leeds and Glasgow.

Among the companies shortlisted to bid to supply the vans are Ford, Land Rover, Nissan and Modec.

A further £50 million of public money will be spent on research into improving the technology, especially the range and life of batteries. It is unclear how the remaining £20 million of the £100 million will be spent.

The Arup report found that electric cars were likely to remain prohibitively expensive for most drivers for several more years, mainly because of the high cost of advanced batteries. It said drivers needed to be educated to consider the whole life cost of a car. While the purchase price of an electric car might be several thousand pounds more than a conventional one, it could be cheaper in the long run because of low operating costs.