James H. Mann, 71, a Washington lawyer for about 30 years before retiring in the mid-1970s and a former government official who was active in Democratic Party politics in Maryland, died of cancer May 25 at George Washington University Hospital. He lived in Poolesville.

Mr. Mann was a graduate of Centre College in his native Kentucky and earned a law degree at Cornell University. He moved to this area about 1940 and was a Treasury Department attorney before spending a year teaching law at the University of Arkansas.

During World War II, he was an assistant general counsel with the Treasury Department before becoming assistant executive director of the War Refugee Board. While holding that post, he became known for his work in compiling and disseminating information regarding the operations of Nazi concentration camps and working for greater efforts on the part of this country to liberate the camps and admit inmates of those institutions to the United States.

He also served as a special assistant to the U.S. ambassadors to the United Kingdom and Argentina and had served as an American representative on a post-war Allied Joint Commission meeting in Switzerland to examine German assets. After World War II, he engaged in the private practice of international law in Washington as a partner in a number of firms.

Mr. Mann was a past executive vice chairman of the Democratic State Central Committee for Montgomery County. He also had been a Democratic Party precinct chairman delegate to a state convention. In 1958, he was an unsuccessful candidate for his party's nomination for Congress. His farm, Rocklands, was the site of an annual party fund-raising auction.

Survivors include his wife, Margaret Blackwell Mann of Poolesville; two daughters, Margaret M. Drachsler of Washington and Judith M. Konig of Williamsburg; a sister, Margaret Cunningham of Louisville and two grandchildren.