Luxury car firm Porsche said Tuesday it will mount a legal challenge to a plan to more than triple the charge for "gas guzzling" vehicles entering central and west London.
London Mayor Ken Livingstone said this month he wants to increase the daily rate from eight pounds to 25 pounds for high-polluting cars, including high performance sports cars and sports utility vehicles.
But Porsche Cars GB's managing director Andy Goss said such an increase "is quite simply unjust".
"Thousands of car owners driving a huge range of cars will be hit by a disproportionate tax which is clear will have a very limited effect on CO2 emissions."
Goss, who claimed the price hike would also hit businesses and make foreign firms and individuals "think twice" before investing in London, said he would write to Livingstone this week and give him 14 days to reply.
"If the mayor fails to respond to Porsche's letter or refuses to reconsider his plans, Porsche intends formally to submit its application for judicial review," he added.
The new charging regime will begin on October 27 -- provided Livingstone is re-elected in a May 1 vote.
It will apply to vehicles emitting more than 225 grammes of carbon dioxide per one kilometre, as well as those registered before March 2001 which have engines larges than 3,000 cc.
Vehicles that emit less than 120g of CO2 per kilometre will get a 100 percent discount.
Transport for London, which runs the five-year-old congestion charge scheme, estimates that 17 percent of the cars currently being driven in the congestion charging zone would be liable and two percent for discounts.
At his weekly news conference Tuesday, Livingstone said he found it "bizarre" that only one car in Porsche's range would be compliant with the proposed new standards for the congestion charge zone.
"They have had years. They know what's happening in the world. Some car manufacturers are full steam ahead to make their cars smaller and safer but not these guys," he added.
Livingstone -- who this month introduced a 200-pound-per-day charge for the heaviest polluting lorries -- found support from environmental group Friends of the Earth.
Its director Tony Juniper said the German automotive sector was "desperately resisting the strong measures needed to tackle the car industry's contribution to climate change".
"Instead of spending time and energy battling these popular initiatives, such as the congestion charge, it would be more appropriate for Porsche to put its effort into making a new generation of much less polluting vehicles."
But the president of motoring group the Automobile Association, Edmund King, said they were concerned that larger families with people carriers or estate cars would also be hit by the "extortionate" charge.
"These families in London tend to do lower mileage, use public transport more and keep their vehicles longer," he said.