German automaker Porsche has launched a formal legal challenge to London Mayor Ken Livingstone’s scheduled tripling of the city’s congestion fee for the most-polluting vehicles. The increase, slated to take effect in October, would raise the fee for the most-polluting vehicles entering the city center to about $50 a day from $16 now. Livingstone and the city’s transportation department have said the fee helps decrease carbon emissions and other pollution by encouraging fewer of the dirtiest cars from entering the city. Porsche argues Livingstone doesn’t have the legal authority to implement the increase and has said in court documents that it expects its U.K. sales to fall by about 11 percent if the higher charge is implemented. However, a survey of city residents by Transport for London revealed that about 61 percent of Londoners support the fee increase. “It’s high time Porsche stopped fighting popular initiatives and started manufacturing cleaner vehicles,” said Tony Juniper of Friends of the Earth.