Government plans for pay-as-you-go motoring have been criticised as "crude, unworkable and clumsy".

The Department of Transport is looking at a nationwide congestion-charging system that would by law make it compulsory for all vehicles to be fitted with a 'black box' meter that would record every mile driven.

The meters, costing about £100 each, would be a sophisticated form of tracking device, recording not only the number of miles covered but also the route taken and the time of day.

This would enable the introduction of variable charges, with a higher levy for driving at peak times.

More than 400,000 lorries are to be equipped with a similar device by 2008.

There are 30 million vehicles on Britain's roads and a pay-as-you-go taxation system would raise billions of extra pounds for the Chancellor.

Only recently Oxfordshire County Council's executive revealed that the Government could be introducing tolls on the A34 in an attempt to curb congestion.

But the prospect of usage charges for every motorist has not excited Oxfordshire's legislators.

"Technology is a wonderful thing, but the kind of sophisticated equipment needed to make such a system work has all the makings of a nightmare," said councillor David Robertson, the executive member for transport on Oxfordshire County Council.

"A whole new tier of civil servants would be needed to administer the operation, sending out monthly bills and chasing defaulters at a time when the Government has announced plans to cut the number of bureaucrats by thousands.

"This method of taxation would lead to social exclusion, hitting the poorest members of society, reducing their ability to socialise by making it impossible for them to afford to run their cars. What's more, it seems unworkable to me."

Oxford West and Abingdon Liberal Democrat MP, Dr Evan Harri,s believed that the answer lay in a tax that targeted polluters.

"Car tax should be abolished and taxes should be raised through the petrol pump," said Dr Harris.

"Highest taxes would be paid by drivers using the dirtiest fuel and owning the largest cars.

"This system would have the benefit of rewarding the environmentally-conscious, encouraging people to buy smaller cars."

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