Porsche has said it will take the mayor of London to court if he does not amend his proposed changes to the congestion charge.
The mayor announced last week that all cars that emit more than 225g of carbon dioxide (CO2) per kilometre will be charged £25 to enter London.
Previously such cars were charged £8.
All but one of Porsche’s current range of sports cars and SUVs emit more than 225g/km.
Now the carmaker has said it will make an application for judicial review of the proposed changes, which it called “unfair and disproportionate”.
“A massive congestion charge increase is quite simply unjust,” Andy Goss, managing director of Porsche Cars GB, said.
“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.”
Porsche said it will be writing to the mayor, Ken Livingstone, this week.
The mayor will then have 14 days to respond.
If he fails to respond or refuses to reconsider his plans, Porsche said it will submit an application for judicial review at the Royal Courts of Justice.
“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 Goss said.
“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.”
The mayor’s office immediately went on the offensive: "Porsche's threatened legal action is a double attack on Londoners.
"First Porsche is trying to deprive Londoners of their democratic right to decide whether they want gas guzzling and polluting cars to drive in London when there is absolutely no need for them to do so,” a spokesperson for the mayor said.
“Second it is trying to impose on all Londoners unnecessary levels of pollution and greenhouse gases by a tiny minority.
"No one is allowed to throw their rubbish in the street and Porsche should not be allowed to impose gas-guzzling polluting cars on Londoners who do not want them."