Christopher Edley, dean of the UC Berkeley School of Law, will resign from his position on Dec. 31, the campus announced Monday.

Edley, who will be on medical leave starting Monday, had surgery for prostate cancer and will need further treatment, according to the campus. Following his resignation, he will continue to focus on “social policy challenges” and remain a Boalt faculty member.

Edley has served as dean of Berkeley Law since 2004 and helped expand its student financial aid program to keep tuition rates affordable, said George Breslauer, UC Berkeley executive vice chancellor and provost, in a statement Monday. Edley has also been a special adviser to UC President Mark Yudof.

Edley redefined Boalt’s financial model and raised “unheard of” amounts of money, according to former Berkeley Law dean and current professor Jesse Choper. He also expanded the faculty and modernized the school’s facilities.

“Transformative is one of those overused, trendy words, but that’s what his work was — transformative,” Choper said.

Edley also headed a UC expansion into web-based learning as chair of the UC Online Instruction Pilot Project, which proposed creating 25 to 40 online classes that would serve as large general education courses.

“He came from high-level politics and brought incredible energy and vision,” said Berkeley Law professor Robert Berring.

On a national scale, Edley has tackled educational analysis as part of the federal Equity and Excellence Commission. He has also held White House policy positions under former presidents Jimmy Carter and Bill Clinton and was on the U.S. Commission on Civil Rights.

He also collaborated on a February report that looked at national trends of rising student debt and dropout rates for students in institutions of higher education.

Following his resignation, Edley will continue to focus on education reform and how to combat deficiencies in the K-12 school system.

Gillian Lester, a professor at the law school, will serve as acting dean for the 2013-14 academic year while the campus searches for a full-term dean.

“We are all immensely grateful to Chris for his transformative impact on the School of Law,” Breslauer said in the statement. “Beyond the material achievements, he has taught the School to ‘think big — very big’ and has demonstrated to us all that the previously unimaginable can indeed be realized.”