If Gifford Miller is elected mayor, he will attempt to institute a commuter tax that would exempt low-income workers and place the heaviest burden on wealthier commuters.

In his first major policy speech since declaring his candidacy, Mr. Miller, the speaker of the City Council, outlined a number of transit-related proposals. The proceeds of the proposed commuter tax, which he said would generate $8 billion in revenue over the next five years, would go to mass transit.

The plan, however, hinges on some improbable developments, principal among them its winning a stamp of approval from reluctant lawmakers in Albany.

“What we need to do is find a steady stream of revenue,” Mr. Miller said during a phone interview yesterday afternoon. “The commuter tax is a logical stream of revenue. The commuters come in, use our subways, and should be contributing something.”

Mr. Miller blasted Mayor Bloomberg for not doing more to address the problems at the cash-strapped Metropolitan Transportation Authority or to fix the subway system, which has had signal and track problems in recent months. He said that under Mr. Bloomberg, the subways were “teetering on the edge.”

Yet even an audience member at the event, held by the Greenwich Village-Chelsea Chamber of Commerce, pointed out that the mayor has “infinitesimal” control over the state-run MTA.

Mr. Miller’s proposal differs from the commuter tax that was repealed in 1999 on two fronts. First, it funnels the money directly to mass transit instead of into the city’s massive budgetary pot. And second, it relies on a four-tiered tax rather than on the 0.45% flat rate that all commuters pay on their income.

The plan would exempt anyone making $25,000 or less. It would then institute rates of 0.25% on those making between $25,000 and $75,000; of 0.4% on anyone earning up to $200,000, and of 0.57% on anyone making more than $200,000.

That means that someone making $85,000 a year, say, would pay about $340 a year.

The main obstacle for Mr. Miller is that Albany has already rejected the idea of reinstituting the tax and seems no more poised to act on it now. Even the speaker of the Assembly, Sheldon Silver, who like Mr. Miller is a Democrat from Manhattan, agreed to the repeal in 1999.

A senior fellow at the Manhattan Institute, Steven Malanga, said it was easy for mayoral candidates such as Mr. Miller to make proposals that have little chance of winning the necessary approval.

“The shape of the proposal is irreverent unless Miller has a formula for getting this passed by the state Legislature, which has refused to reinstate it,” Mr. Malanga said. “Why is this proposal more likely to pass than the others? Let’s face it: Rudy Giuliani argued for the reinstatement of the tax, Mayor Bloomberg has argued for it, and yet it hasn’t occurred.”

In addition to the commuter-tax proposal, Mr. Miller, one of four candidates seeking the Democratic Party’s nomination to challenge Mr. Bloomberg in November’s general election, said the MTA should “freeze” expansion until it gets its finances in order.

He said the MTA should shave 10% of its workforce and delay construction of the East Side Access link, which would connect the Long Island Rail Road to Grand Central Terminal.

He did, however, say that if his proposal to generate revenue were accepted, then the MTA should invest in building a Second Avenue subway line. Among New Yorkers who would benefit from that long-term, $16 billion project are those who live in Mr. Miller’s Council district and those who live in Mr. Silver’s Assembly district. He also proposed an extension of the no. 7 subway line from Times Square, where it now stops, to the far West Side of Manhattan.

Mr. Miller also proposed creating an independent inspector general to root out wasteful spending at the MTA, and he pressed again for the MTA to seek new offers for the air rights to build on the West Side of Manhattan, where the New York Jets want to build a new football stadium.

A spokesman for the MTA, Thomas Kelly, issued a statement to The New York Sun that read: “It is clear that Speaker Miller has no familiarity with the MTA’s $8 billion budget or an understanding of the support staff needed to provide 8 million trips each day.”

A spokesman for Mr. Bloomberg’s campaign, Stuart Loeser, said that despite Mr. Miller’s remarks, the mayor has dedicated significant resources to the MTA.

“Under Mike Bloomberg, New York City is paying for a subway line extension for the first time in history and made the largest contribution to the MTA capital plan ever – $2.2 billion, or five times bigger than before,” Mr. Loeser said. The former reference was to the no. 7 extension.

The campaign of Rep. Anthony Weiner of Queens, who is one of the three other Democratic mayoral candidates, said the commuter tax was “something that has been talked about for years.”

“Congressman Weiner favors it, but his emphasis in this campaign is on a more creative, forward-looking approach,” Mr. Weiner’s spokesman, Anson Kaye, said.

Mr. Miller plans to roll out several policy plans in the coming weeks. When asked how often he takes the subway, he conveniently noted that he had taken it to the event and said he rides it regularly.

“I take the subways on a regular basis,” he said. “I’ve been riding the subways all of my life.”