One of Mayor Bloomberg’s political rivals said yesterday that the city could end up paying far more to build a stadium for the Jets than the $300 million the administration has said it would commit.

During a speech at Columbia University’s law school, the speaker of the City Council, Gifford Miller, said the Sports and Convention Center on Manhattan’s West Side could cost the city up to $1 billion. Mr. Miller, one of four Democrats running to replace Mr. Bloomberg, said not only will the city forgo collecting property taxes or so-called “payments in lieu of taxes,” but it could get stuck with the state’s $300 million share of the project. He also cited “hundred of millions of dollars” in infrastructure costs for other amenities outside the proposed 75,000-seat structure.

“When you really add it all up, what New York City could be looking at is close to $1 billion in costs to build a football stadium,” Mr. Miller said.

Jets officials said the speaker’s math was faulty. The Jets’ vice president of development, Thad Sheely, said the city would not enter into an agreement without a state commitment of $300 million. “Unfortunately we’re being swept up in Election Day politics,” Mr. Sheely said.

A professor of economics at Smith College, Andrew Zimbalist, said it wasn’t inconceivable that the city’s costs could run to $1 billion but said potential revenue from the stadium should also be considered.