TRENTON — Gov. Christie's proposal to renovate the Statehouse gained a key stamp of approval Thursday, as the New Jersey Economic Development Authority approved borrowing $300 million to finance the project.

Lawmakers from both parties, including some gubernatorial candidates running to succeed Christie in this year's election, have argued that deeply indebted New Jersey cannot afford the project and should focus its priorities elsewhere.

Opponents also contend that only the Legislature, not the executive branch, has the authority to issue such debt.

Christie, who will leave office in January, says the executive portion of the Statehouse is a "firetrap." He says there hasn't been a comprehensive renovation of the executive portion in 60 years. The oldest part of the Statehouse was built in 1792.

The final maturity of the bonds will not exceed 30 years, according to an Economic Development Authority (EDA) memo. The authority is chaired by Thomas P. Scrivo, Christie's former chief counsel.

Through a competitive bidding process, the Treasury Department and Attorney General's Office selected the law firm Chiesa Shahinian & Giantomasi PC as bond counsel, according to the memo.

Jeffrey S. Chiesa, a partner at the firm, is Christie's former attorney general. The governor also named Chiesa as the state's overseer of Atlantic City. Chiesa's law firm has billed the state for $1.1 million for work in Atlantic City, according to newly released invoices.

Thursday's vote by the EDA came after an obscure board of Statehouse staffers advanced the project last month. The State Capitol Joint Management Commission will lease the building to the EDA for $1.

The EDA will then rent the Statehouse to the commission at a high enough rate to pay back the interest on the bonds.

During the renovations, the governor's office and departmental employees who work in the Statehouse will move to a state building down the street.