The re-assessment comes as ministers become seriously rattled by the furore over the building of the Newbury by-pass. Even strongly pro-car Tory MPs concede that road-building will lose the party votes in its south of England heartland in the next General Election. Robert Key - the former roads minister who once declared "I love cars of all shapes and sizes" - acknowledged last week that new roads may be alienating the electorate.
But ministers have still not given a formal, detailed response to the report of the Royal Commission on Environmental Pollution which, 15 months ago, called for "a fundamental change of culture". It said that petrol prices should be doubled and road-building halved.
Both environmentalists and motorist organisations are increasingly angry at the Government's failure to reply and the row will intensify on Thursday when the Prime Minister's personal group of environmental advisers, including Sir Crispin Tickell, will publicly call on him to ensure a response.
Senior government sources say that the Chancellor, Kenneth Clarke, regards the report's recommendations as a "nightmare" and has successfully blocked a point-by-point response
The White Paper will replace one published in 1989, which doubled the size of the road programme. Entitled "Roads for Prosperity", this enshrined the then Prime Minister's enthusiasm for "the great car economy" and predicted that vehicle use would double in a generation.
The new document, whose timing has yet to be decided, reflect Transport Secretary Sir George Young's greater commitment to public transport. Already the roads programme has been sharply scaled back.
Labour's transport spokeswoman Clare Short will tomorrow join those calling for more restrictions on car use.
"We must cease to expect to be able to drive into the centre of towns and cities and to take our cars wherever we go," she will tell the Transport Policy for Britain conference.
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