Fifteen Harvard law students will work as clerks in Southern law offices and as advisors to civil rights organizations in Northern cities this summer.

The Harvard contingent, almost twice as large as last year's, will join 150 recruits from other Northern law schools. They hope to ease problems of under staffing in the offices of civil rights lawyers, according to Elizabeth Holtzman 31, who is coordinating the project at Harvard.

Southern lawyers anticipation an "overwhelming burden of cases" this summer because of new voter registration projects and suits arising from violation of new civil rights laws. The law students will relieve their employers of research duties and other mechanical tasks.

The students will be employed by the American Civil Liberties Union, and by Negro lawyers in most of the states of the Deep South.

Volunteers working in Northern cities will be attacked to community-development projects like the Boston SDS venture on Dudley St. They will be available to civil rights leaders and to local residents for consultation and advice.

The project is sponsored by the national Law Students' Civil Rights. Research Council, an association of law students originally devoted to study of problems confronting southern civil rights lawyers. The addition of the Northern projects this year has expanded the summer program by nearly 100 participants.