A plan being pushed by a vocal opponent of the mayor’s congestion-pricing proposal would have taxi riders paying $4 extra each trip rather than forcing drivers to pay an $8 fee to enter Manhattan below 60th Street.

Assemblyman Richard Brodsky, whose district includes Westchester County, says he has brought together a coalition of 30 lawmakers in the Assembly who would support the taxi fee as an alternative method of reducing congestion and raising money to fund mass transit improvements. Many elected officials from the boroughs outside Manhattan and from surrounding counties say their constituents would unfairly bear the cost of the congestion plan, which is predicted to raise $491 million a year for public transportation.

The managing director of the League of Mutual Taxi Owners, Vincent Sapone, said the taxi fee proposal would cause “thousands of people” to lose their jobs.

“Is he out of his mind?” Mr. Sapone said. “You’re talking about a $2 billion industry that he’ll destroy.”

In addition to a surcharge on taxis, Mr. Brodsky’s plan includes an increase in the number of taxi stands in the city, and a hike in traffic fines. The $4 increase would raise the current $2.50 “drop charge” to $6.50, but the regular fare would be reduced to 35 cents for each fifth of a mile from 40 cents. The additional money would be used to pay for public transit improvements.

An artist who takes taxis back to Jersey City from his job in downtown Manhattan, William Phair, said that if cabs charged $6.50 just to get in the door, he would stop using them.

“That’s way too expensive,” Mr. Phair said.

Mr. Brodsky’s proposal comes at a time when the future of Mayor Bloomberg’s congestion-pricing plan is uncertain. Several Albany legislators have expressed pessimism that the backers could muster enough votes to pass the plan. Lawmakers are waiting for the City Council to pass its own legislation before they introduce a congestion-pricing bill, according to Dan Weiler, a spokesman for the Assembly speaker, Sheldon Silver.

A spokesman for the mayor’s office, John Gallagher, called Mr. Brodsky’s proposal “pointless,” saying in an e-mail message: “It won’t reduce congestion and it won’t raise revenues to pay for mass transit improvements.” In the congestion-pricing plan backed by Mr. Bloomberg, taxi riders would have to pay a $1 surcharge if they began or ended their trips in the congestion zone.

A state senator whose district includes commuters from Brooklyn and Staten Island, Diane Savino, said she “absolutely supports” Mr. Brodsky’s proposal.

“Richard came up with a thoughtful proposal that would allow us to raise the money necessary and reduce traffic,” Ms. Savino said. “It places the burden on the people who can afford it the most.”

A spokesman for the Metropolitan Taxi Board of Trade, Michael Woloz, called Mr. Brodsky’s fee plan “unfair and backwards.”

“Taxis are a vital part of the solution on reducing congestion in New York City,” Mr. Woloz said. “They are a major part of why only 22% of Manhattan residents own a private car, which is the lowest level in the United States.”

Akturk Ertugral, who has driven a cab for more than 20 years, said he worried the plan would cut his business in half.

“We lose enough fares already as it is,” Mr. Ertugral said. “I’d rather have them lower our prices.”

Mr. Brodsky is pushing his plan in the final month before a March 31 deadline would effectively disqualify the city from $354 million in federal funding if the City Council and the Legislature do not pass congestion-pricing legislation. At the behest of Mr. Bloomberg and lawmakers in Albany, the Metropolitan Transportation Authority released its $30 billion five-year capital spending program on Wednesday, weeks ahead of schedule, in order to avoid a last-minute effort to pass legislation ahead of the federal deadline.

“It wasn’t designed to be good for the industry, any more than it was designed to bad for the industry,” Mr. Brodsky said in an interview with The New York Sun yesterday. He said taxi congestion accounts for “40% of the problem.”

Officials at the MTA are relying heavily on future congestion-pricing revenues, anticipating $4.5 billion for long-delayed mega-projects such as the Second Avenue Subway and the Fulton Street Transit Center.

Even with congestion pricing, the MTA would have a $9.5 billion gap in its budget, raising concerns that the authority would have to continue scaling back projects as prices for construction and materials increase.