Just before the biggest world population conference in 10 years, White House policy aides have alarmed some demographers by proposing that the United States curtail family-planning support.
It comes as the International Conference on Population prepares to meet in Mexico City Aug. 6-13, the first such meeting in 10 years. Meanwhile, demographic figures forecast hungry world population will rise from 4.6 billion at present to 10.3 billion in 2050.
The White House Office of Policy Development, which often sets administration policy, has circulated a study advocating the cutoff of US assistance to population control programs that practice or advocate abortion.
The position paper, prepared for delivery before the Mexico City conference, charges that in ''the 1960s and 1970s, doomsday scenarios took the place of realistic forecasts, and too many countries pursued population control policies that have had little impact on population growth.''
It criticizes the Carter administration's ''Global 2000'' report, and says that ''this administration in 1981 repudiated its call for more governmental supervision and control.''
The White House position pleases conservative groups, who have never approved of government-supported population control. But cries of alarm from sections of the scientific community have followed the report.
''There is a clear-cut implication in the White House draft that voluntary family-planning programs do not work. . . . In fact, the record of family-planning programs is encouraging,'' said Jane Menken, president-elect of the Population Association of America.
''Most of the population of the third world lives in countries that want slower rates of population growth and are trying to achieve them,'' said Thomas W. Merrick of Georgetown University.
''The draft paper (from the White House) reflects a surprisingly unbalanced interpretation of our current knowledge. . . . The President has been let down and seriously embarrassed,'' said Michael S. Teitelbaum of the Alfred P. Sloan Foundation.
The White House policy position paper is not a final word and does not necessarily set administration policy. President Reagan's advisers are aware of the religious controversy over birth control, family planning, and abortion. In their draft study they argue that population control has only limited value.
But sharp replies have come from some in the scientific community.
''There is no obvious economic or humane justification for the policy change proposed in the position paper,'' said Paul Schultz of'Yale at a press conference organized for Congress by Rep. John E. Porter (R) of Illinois and Rep. Sander M. Levin (D) Michigan.
problems are an increasing burden for governments
worldwide: Congress has spent weeks on the pending immigration reform law, designed to control Mexican entry.
China, with a population of over 1 billion, has again taken drastic steps to check expansion.