LONDON —Mayor Ken Livingstone of London said he will more than triple the daily traffic congestion charge for big cars in the center of the city to $47.43 starting next year, in a bid to improve air quality.

The plan comes as a group of residents in west London said they are organizing a protest over the extension of the mayor’s congestion charge into their neighborhoods beginning next week.

Mr. Livingstone said owners of large cars and sport-utility vehicles, who now pay about $15 a day in the congestion zone, will pay about $49 from June or July of 2008. Owners of big vehicles who live within the zone will lose their resident discount and will also pay 25 pounds. Residents now pay about $1.55 a day with the discount when they drive within the zone.

“We think this will be a sufficient deterrent to make people shift into less-polluting cars,” the mayor said yesterday at his weekly news conference. He said in November he was studying the fee increase, and that it might take effect in 2009.

Mr. Livingstone, who says climate change is the biggest issue facing Londoners, introduced the congestion charge in the central city in 2003 to reduce traffic, improve air quality, and raise cash for public transportation. The charging zone will be extended February 19 to take in Kensington & Chelsea, Knightsbridge, and Notting Hill. Many residents are opposed to the move.

“The mayor of London should call a halt to this costly, unnecessary and damaging tax on west Londoners,” said Nick Botterill, a member of the Hammersmith & Fulham Council, in a statement sent by e-mail yesterday.

Opponents of the charge, including the West London Residents Association, will gather a convoy of vehicles for a “go-slow” protest through west London on February 17.

Mr. Livingstone played down the protest, saying the congestion charge has been “the difference between keeping London moving and gridlock.” He also said traffic in the zone has begun to increase and the rate of congestion reduction has slowed. Congestion last year was reduced by 8% compared with 30% in the year after the charge was introduced, he said.

According to the mayor’s plan, owners of vehicles that emit more than 225 grams of carbon dioxide a kilometer, the highest category for British vehicle tax purposes, would pay the maximum charge of about $49 a day.

The group ranges from Peugeot 407 station wagons with 3.0-liter gasoline engines to BMW 760Li and Jaguar XJ sedans with V8 engines to Land Rover Discovery and Range Rover sport utilities, according to the Department for Transport Web site.

There are no plans to increase charges for smaller vehicles, Mr. Livingstone said.

The Association of British Drivers, which has gathered 1.3 million signatures on a petition to oppose British road fees, condemned the mayor’s plans.

“It’s absolutely disgraceful, it’s picking on people, and it’s just another way of raising tax on motorists,” said Nigel Humphries, a spokesman for the association.

Mr. Livingstone owns a Toyota Prius, a low-pollution vehicle that’s powered by a gasoline engine and electric motor. The Prius, and similar models such as the Honda Civic Hybrid are exempt from the charge.