Reagan administration health officials are considering reorganizing a key birth control agency, a proposal critics see as another administration attack on family planning efforts.

The agency, the Office of Family Planning, in Rockville, is now part of the Health Services Administration of the Health and Human Services Department. Under a "draft" proposal that has been widely circulated in the department, it would move to HHS headquarters and become part of the Office of Population Affairs, headed by Marjory Mecklenburg, a prominent anti-abortion figure.

The Office of Family Planning is responsible for dispensing grants to family planning groups and clinics; this fiscal year the grants totaled $1.2 million.

Rep. Henry A. Waxman (D-Calif.), chairman of the House Energy and Commerce subcommittee on health and the environment, has asked Dr. Edward N. Brandt, assistant secretary of HHS for health, to block the move, calling it "a political assault" on a program already "politicized" and "harassed" by Reagan aides.

Rep. Patricia Schroeder (D-Colo.), chairman of the House Post Office and Civil Service subcommitte on civil service, and Sen. Robert T. Stafford (R-Vt.) also wrote HHS Secretary Richard S. Schweiker this week, questioning the move and its "political" orientation.

The situation is complicated, because Mecklenburg is already acting head of the family planning office, as well as acting deputy assistant secretary for population affairs.

Still, says Washington Report on Medicine and Health, a newsletter, the move would "cement her control" over family planning. Mecklenburg is also director of the Office of Adolescent Pregnancy Programs.

The situation is further complicated because the draft proposal bears Brandt's typed signature, but Brandt said through an aide that he hasn't seen it and that it is "only one of several" possible proposals for reorganizing the Public Health Service.

The draft argued that the move would consolidate population affairs, reflect "the high priority nature of these vital health programs" and provide "consistency" in interpreting administration policy."

Stafford, Schroeder and Waxman all questioned the wisdom of putting a health service directly under a political appointee. Schroeder asked Schweiker to justify the move in terms of costs, policy and effectiveness.

Waxman saw it as the latest in a series of moves to weaken family planning.

He cited the administration's unsuccessful move to fold family planning funds into block grants to states; several audits of family planning clinics by HHS that the clinics' proponents viewed as harassment, and a proposed HHS rule that would require federally funded clinics to notify parents when they prescribe contraceptives for teen-age girls.

"All these things are calculated to discourage teen-agers from using these services," Waxman said. "Now comes this move to put them under Mrs. Mecklenburg, who has no public health credentials and whose prior anti-abortion activities may lead to further harassment."