By Daniel Wiessner and Joseph Ax

NEW YORK (Reuters) - Aspiring lawyers in New York State must perform 50 hours of free legal work to gain entry to the state bar under a first-of-its-kind requirement handed down on Wednesday aimed at expanding access to the legal system for the poor.

The rule, written by New York's top-ranking judge, takes effect in 2015 and applies to all future law school students and those currently in their first or second years. Existing third-year students are exempt.

Chief Judge Jonathan Lippman estimated the requirement will add as much as 500,000 hours of pro bono service each year. Only 20 percent of the need for legal services is being met in New York, he said, even though state officials this year agreed to double funding for legal service programs to $25 million.

"No matter how much money we're able to get through public funding, a large part of this has to be pro bono service on the part of the bar," Lippman said in an interview.

Advocates for legal aid for the poor applauded the rule, which is unique to New York State.

"I think that is a reflection of the sense of urgency that Judge Lippman and his committee have about this crisis in access to legal services, which is really negatively impacting the justice system and public faith in the system," said Esther Lardent, executive director of the Washington-based Pro Bono Institute.

Under the new rule, first proposed in the spring, pro bono service is defined as providing "law-related" services to low-income people, non-profit organizations, civil rights groups or any government entity.

But since the rule was revised to include work already commonly done by law students, the net amount of new legal work provided at no cost could be lower than Lippman's estimated 500,000 hours.

Those revisions came after the state's legal establishment, caught by surprise by Lippman's initial proposal, raised concern about the cost to law schools of setting up new pro bono programs on top of existing ones, such as already-established legal clinics staffed by law students.

The final regulation allows those clinics to count toward the requirement, even though students typically receive academic credit for those programs.

"We didn't want to force people to leap tall buildings in a single bound to perform this service," Lippman said. "(But) pro bono is a part of the core values of our profession. Lawyers, or those aspiring to be lawyers, have to embrace those core values."

Last year, there were 15,000 applicants to the New York bar.

The requirement comes as law students, many of whom graduate with heavy debt, face an uncertain job market.

A June report from the National Association of Law Placement found that fewer than two-thirds of 2011 graduates had landed a job that required an attorney license, the lowest percentage since the group began its annual survey in 1974.

(Editing by Dan Burns and Doina Chiacu)