The sniping against the London congestion charge continues unabated in the face of all evidence that the measure, introduced by Ken Livingstone earlier this year, has been a success, reducing traffic levels and making London a better place in which to live.
The latest complaint is that Capita, the contractor operating the charge, is making insufficient profits, though this might also be read as a sign that the charge is effective in keeping cars out of London. The line of attack changes to fit the times. Initially, opponents warned of gridlock and chaos in the areas surrounding the congestion-charge zone, and that the charge undermined the fundamental right to travel and was a threat to civil liberties.
The complaints proved hollow, leaving Steve Norris, hapless Tory mayoral candidate, looking foolish when he promised to abolish the scheme on his first day in office. Legal threats have melted away, and the Sod-U-Ken website is now a sad, abandoned lay-by on the information superhighway, its homepage advertising a protest by cab drivers held a month ago.
Now Conservative members of the Greater London Assembly focus almost exclusively on the economic argument. Talk to any small shopkeeper just inside the zone, they say, and he or she will tell you that the congestion charge has wrecked their business. The London Chamber of Commerce claims that three-quarters of its members have experienced a downturn in business, for which it blames, in part, the congestion charge.
But they are wrong. Transport for London has commissioned research to assess the impact of the congestion charge on local businesses. Its preliminary findings do, indeed, confirm that central London has been suffering a more serious decline in business than outlying areas. However, this loss started before the introduction of the congestion charge on 17 February. Other, earlier factors include a decline in tourism caused by the build-up to the Iraq war and, crucially, the closure of the Central Line for nearly three months after the Chancery Lane accident on 25 January.
Transport for London found that the proportion of shoppers likely to travel to central London by car is small. A mere 1,000-2,000 cars, carrying a maximum of 3,000 potential shoppers, may have been discouraged by the charge, an insignificant number in relation to the overall "footfall" for central London's shops.
None of this will stop the shopkeepers whingeing, though. During the recent hot weather, their representatives trooped into television studios to say the heatwave was devastating business. When the next set of trading figures emerged, it was clear that the opposite was true - business boomed in the sweltering temperatures.
Expect further sallies in the propaganda war against the congestion charge over Livingstone's plan to extend the zone westwards. A recent poll suggested that a small majority is against this, although residents of Westminster and Kensington & Chelsea were supportive, possibly because they realise they will get a 90 per cent discount, paying just 50p per day, instead of £5, to drive within the whole zone.
Either way, the charge is here to stay. But other British cities hoping to follow London will need a mayor with a thick skin and a resolute sense of purpose.
Christian Wolmar's latest book is Down the Tube: the battle for London's Underground (Aurum Press)