The head of Volvo Cars Europe yesterday wrote to London Mayor Boris Johnson urging him to eliminate the "apparent injustice" of giving a free ride into London to the owners of hybrid automobiles. Volvo argued that although the hybrid preference may have made sense in the past, advances in internal combustion technology have made conventional engines cleaner than ever.

"It is Volvo's belief that, in its current structure, the London congestion charge unfairly benefits hybrid-powered cars at the expense of drivers choosing normal internal combustion-powered ones with similar levels of emissions," Stuart Kerr, Regional President for Volvo Europe wrote. "We now find ourselves in a situation where conventional cars can deliver equivalent, and in some cases, better levels of emissions than the hybrid cars that still receive an exemption from the charge."

In 2003, London began imposing a charge, now £8 (US $13), on drivers entering the downtown area. Then-Mayor Ken Livingstone exempted hybrid vehicles such as the Toyota Prius so that the tax, which generated £268 million (US $439 million) in revenue in 2007, would appear to be an environmentally friendly program. Livingstone promised this proposal would deliver large reductions in carbon dioxide, and even proposed an extra £25 (US $40) tax on certain sports and luxury cars based solely on CO2 emissions. Upon taking office, Mayor Johnson killed the extra CO2 tax.

Carbon dioxide is a naturally occurring gas generated by animals that is essential to life. Roadside measurements of oxides of nitrogen over a period of four years showed congestion charging in London did nothing to reduce these pollutants, which are actually harmful to air quality.

Volvo sees a problem that the charge is not based on results, but a favored technology. The company insists that thirteen non-hybrid car models on sale in England best the celebrated Toyota Prius, which creates carbon dioxide at a rate of 105 grams per kilometer driven. The list of "cleaner" cars includes Volvo's own S40 DRIVe, a similarly sized vehicle that, unlike the Prius, is subject to the congestion tax. Worse in Volvo's view, models like the C30 Sportscoupe and V50 Sportswagon generate 85 percent less carbon dioxide at the tailpipe than the exempt Lexus 400h hybrid.

"I appreciate that the removal of the congestion charge for all low-emitting cars would have considerable financial implications for Transport for London but at Volvo, we believe in one rule for one, one rule for all," Kerr wrote.

Although Mayor Johnson has made statements favorable to removing the congestion tax, his predecessor locked in a contract giving IBM the right to collect the charge until the year 2014 unless city exercises a buyout clause that would cost taxpayers millions.