Charging President Carter with failing to offer any "realistic" alternatives to abortion, six major family planning and health groups urged him yesterday to adopt a three-year, $1.7 billion program to prevent more than a million unwanted pregnancies a year.

The six called the administration anti-abortion stance "harsh" and "abhorrent" for proposing to deny Medicaid abortions to "the poor and minorities."

During his election campaign Carter both called abortion "wrong" and declared, "I think we ought to do everything to have better education, family planning, contraceptives, if desired."

But the six groups told a news conference there has been "no sign of an administration family planning initiative," and "neither the White House nor HEW" - the Department of Health, Education and Welfare - has offered anything but "ineffective" alternatives to abortions, such as increasing adoptions.

The six are the Planned Parenthood Federation of America, American Public Health Association, National Family Planning Forum (the main association of family planning clinics), Population Council, Zero Population Growth Inc. and Great Lakts Family Planning Coalition (government and private agencies in five states).

As the only possible effective alternative to abortion, they said, the federal government should help prevent the nearly 2 million unwanted and accidental pregnancies a year that force women to seek abortions in the first place.

The six offered a detailed proposal to increase federal support of contraception and family planning services, preganancy detection and many related health and research programs.

To fund them, they advocated an increase from the $225 million budgeted in fiscal 1978 to $410 million in 1979, $586 million in 1989 and $783 million in 1981.

"If this money isn't spent, the government will spend five to 10 times that much in medical, social, welfare, educational and other services because of these unintended pregnancies," said Frederick S. Jaffe, president of the Alan Guttmacher Institute, Planned Parenthood's research arm.

"There will be government expenditures one way or the other," he said. "The question is, 'Are you going to spend the money intelligently?'"

Jeannie Rossoff, head of Planned Parenthood's Washington office, said "we are disappointed and outraged" both at the anti-abortion statements of the President and HEW Secretary Joseph A. Califano Jr., and their failure to offer any attack on abortion's root cause, the unwanted pregnancy.

In response to a Supreme Court decision that the government need not pay for elective abortions, HEW has said it will halt all funding for Medicaid-financed abortions as of Monday, when the court's order takes effect.

Several groups have petitioned Supreme Court Justice Thurgood Marshall to postpone that effective date, saying they need time to prepare new legal arguments on the issue.

"We have already made tremendous progress in this country in preventing unwanted pregnancies," Jaffe, main spokesman for the six health groups, said yesterday.

"What we're talking about now is preventing the last 15 per cent. It's very do-able. What is needed is a commitment by the President."

The highest priority target groups, he said, would be the poor and the very young, where unwanted pregnancy is epidemic.

Jaffe called HEW proposals to reduce abortions by increasing adoptions - providing prenatal care for the pregnant women who choose adoption over abortion - a way of "bribing an unfortunate class of women to be breeders for the more fortunate."

Meanwhile, a spokesman for Carter said the President does not plan to change his position on abortion, and was "perplexed" by objections that came last week from some of the women in his administration.

"It's a position he held throughout the campaign," said deputy press secretary Rex Granum. "It's one of the elements on which he was elected and he does not plan to change that position . . . He just doesn't understand that sort of immediate and coordinated reaction to the simple restatement of a position which he's held for the entire campaign."