The planned expansion of the Jacob K. Javits Convention Center came under attack yesterday from elected officials who feel the new designs will leave New York with a second-class facility.

Last week, the state released revised designs for the $1.7 billion convention center expansion, scheduled to begin by late this summer and be completed by 2010. The state has said the plan would cost $1.4 billion.

The new expansion plan will extend the center north along Eleventh Avenue one block to 40th Street, and will increase exhibit and meeting room space to more than 1.3 million square feet. Some of the additional square footage will be achieved by building vertically on the current facility. In addition, the state plans to sell an entire city block to the south of the center for private commercial and residential development to generate additional project funds.

At a public hearing yesterday, Assemblyman Richard Brodsky, a Democrat who heads the Committee on Corporations, Authorities, and Commissions, questioned state and city development officials under oath on the reduced size of the planned expansion, the center’s future expandability, and whether the new space will be in high demand among conventioneers.

Mr. Brodsky, who is running for state attorney general, also said he had questions about the price and the timetable that the state has laid out for the sale of the block to the south of the center.

Another member of the committee, Assemblyman Richard Gottfried, who is the neighborhood’s representative, called the plan “utterly misguided” and said it “looks like it barely has been thought through.”

Earlier this week, Senator Schumer sent a letter to the chairman of the state’s development agency, Charles Gargano, criticizing the current plans as being too small, too costly, and shortsighted.

Mr. Gargano and Deputy Mayor Daniel Doctoroff testified yesterday that the current expansion was the best possible plan considering budget, space, and time constraints. They said the new plan was better oriented to spur development of the Hudson Yards areas, a major development priority of the Bloomberg administration. They also said any major changes to the plan could delay the project considerably, perhaps indefinitely.

Although city and state officials have said previously that the plan is on time, Mr. Doctoroff said delays were caused by “political issues” involving the convention center’s operating corporation and the state’s development agency.

That political dispute reportedly surrounded the former chairman of the convention center, Robert Boyle, who was removed from his post by Governor Pataki in late December. Mr. Boyle had advocated a larger expansion and putting a hotel on the northern end of the center at 42nd Street. Current plans place the hotel between 35th and 36th streets on Eleventh Avenue.

Mr. Brodsky said yesterday that those “bureaucratic” delays caused the development agency to “rush” the current designs.