Opponents of Mayor Bloomberg’s congestion pricing plan fear that a large fee hike just announced in London may be reproduced here.

London Mayor Ken Livingstone, who implemented congestion pricing in 2003, said yesterday there would be new fees to the city’s congestion scheme that will charge drivers of high-emission vehicles such as powerful sports cars and sport utility vehicles nearly $50 to drive into the city, while the standard $16 fee on other cars will be waived for fuel-efficient hybrids. Mr. Livingstone, who has the authority to implement the changes unilaterally, said the new charges would begin in October.

The changes in London are providing fodder for critics of Mayor Bloomberg’s congestion pricing plan, which would have to be approved by the City Council and in Albany. Critics say fees for cars entering Manhattan’s congestion zone, set under Mr. Bloomberg’s plan at around $8, will rise steeply in the future.

“What happened in London will happen in New York,” Assemblyman Richard Brodsky said in a telephone interview yesterday. “I know it’s the next step. They’re trying to raise more money.”

Advocates of congestion pricing here say New York will chart its own course.

A member of the commission that recently recommended a congestion pricing plan to the city and state government, Kathryn Wylde, said that just because New York is seeking to follow London’s lead on congestion pricing does not necessarily mean that the city will adopt the new fees.

“I think we’ll let them once again try it out first,” Ms. Wylde, the president and CEO of the Partnership for New York City, said. “I think we can watch and learn from the various measures that Europe is taking, but I don’t think we can leap into them.”

While the new rules in London aim to reduce greenhouse gas emissions and thereby combat global warming, the New York plan has been promoted as a way to reduce traffic and increase revenue for transit.

“Congestion pricing has to be about congestion,” the chairman of the City Council’s Transportation Committee, John Liu, said. “That’s why it’s called congestion pricing, not pollution pricing.”

“The idea of fees around $50, your jaw drops,” Mr. Liu said. “The opponents of congestion pricing are having a field day with this. It is red meat for them to sink their teeth into.”

If congestion pricing is approved by the state Legislature by March 31, the Bush administration has pledged to contribute $354 million in funding for the plan’s implementation. The deadline is on the same day that the Metropolitan Transportation Authority is scheduled to release its five-year capital plan, which outlines budget and revenue projections for major projects such as the Second Avenue subway line and the No. 7 subway line extension. The speaker of the Assembly, Sheldon Silver, has said the Assembly will not consider a vote on congestion pricing until the MTA makes public its capital plan, which is dependent on revenues from congestion fees.

Messrs. Bloomberg and Silver yesterday called on the MTA to release their plan this month, instead of waiting until the federal deadline.