Car company Porsche is to mount a legal challenge over the decision by London Mayor Ken Livingstone to raise the capital's congestion charge from £8 to £25 for the highest-polluting vehicles.
Porsche said it believed the increase was "unfair" and was making an application for judicial review of the decision.
Andy Goss, managing director of Porsche Cars GB, said: "A massive congestion charge increase is quite simply unjust. Thousands of car owners driving a huge range of cars will be hit by a disproportionate tax which it is clear will have a very limited effect on CO2 emissions."
Porsche said it would be writing to Mr Livingstone this week and that he would then have 14 days to respond to the company.
"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 at the Royal Courts of Justice", the company said.
Mr Goss added: "Not only is this rise completely unfair to many drivers, but it will also damage London based-businesses of all sizes, and successful people from across the world will start to think twice about basing themselves here if they think they are going to be used as cash cows for City Hall (Mr Livingstone's headquarters).
"The proposed increase will be bad for London as a whole and will send out the signal that it is not serious about establishing itself as the best place in the world to do business."
To begin on October 27 this year, the new charging regime will see the £25 charge apply to vehicles emitting more than 225 grams of carbon dioxide per one kilometre, as well as those registered before March 2001 which have engines larger than 3,000cc
Those vehicles getting a 100% discount will emit less than 120g/km.
Of cars currently being driven in the congestion charging zone, 17% would be liable for the £25 charge and just 2% for the total discount.
