Theressa H. Clark, 52 an official of the United Planning Organization and former deputy director of the D.C. Office of Consumer Affairs, died of an internal hemorrhage Nov. 12 at Washington Hospital Center.

Mrs. Clark came here in 1953 and began working for the United Planning Organization in the early 1960s. She was chief of UPO's consumer protection branch and consumer action adviser for Far East Community Services before joining the city government in the early 1970s.

She returned to the UPO as a consumer complaint investigator in 1977. Earlier this year she was named senior citizens program coordinator of the UPO.

Mrs. Clark was a native of Suffolk, Va. She was a graduate of Morgan State College in Baltimore and earned a master's degree in public administration at Southern Illinois University.

She taught high school science courses in Rustburg, Va., before moving to Washington.

She was a member of Michigan Park Christian Church here.

She is survived by her husband, Eddie M. Clark Sr., of the home in Washington; a son, Eddie Jr., a student at Northwestern University: her mother, Phyllis Osborne, of Philadelphia, and two brothers, Rhomie L. Heck Jr., of Hampton, Va. and James R. Heck III, of Williamsville, N.Y.