Sen. Daniel Patrick Moynihan (D-N.Y.), whose call 20 years ago for a national policy on the family was criticized and ignored, says that since then the government has largely eliminated the plight of the indigent elderly while allowing the number of poor children to vastly increase.

In a speech to be delivered Monday at Harvard University, Moynihan says that "the rate of poverty among the very young in the United States had become nearly six times as great as among the old."

"During the '70s, owing in large measure to government transfer programs under Social Security, the problem of poverty greatly diminished among the aged, but intensified among the young," he says.

"No government, however firm might be its wish otherwise, can avoid having policies that profoundly influence family relationships. This is not to be avoided," he says. "It has been argued that the largest single change in the tax code since 1948 is the erosion of the value of the dependent deduction in the income tax, in consequence of which we now tax families with incomes below the poverty line."

"Poverty is now inextricably associated with family structure," he says. "Half of all poor persons live in female-headed households."

While offering few specifics for a family policy, Moynihan calls for a sizable increase in the income tax deduction for dependents.

Saying that, as a society, "We value self-sufficiency and we are offended by poverty," Moynihan contends that "It follows that we should not tax individuals, much less families, to the point where they are officially poor and potentially dependent. We now do that."

He also says, "More than three-fourths of median family income in 1948 was exempt from federal tax," and asks, "Was this not a powerful national family policy? It costs money to raise a family, and the federal government chose not to tax most of the income so required. This is no longer so."

In 1983 "less than one-third of the median family income was exempt," he says, adding that a poor family is now "subject to tax."

The senator, who is the ranking Democrat on the Senate Finance Committee's subcommitee on income-maintenance programs, also contends that basic welfare payments should be indexed to inflation.

Moynihan criticizes the book "Losing Ground" by Charles Murray, which argues that social programs have hurt rather than helped the poor. He is particularly critical of Murray's assertion that increased social spending leads to more social problems:

"From 1969 to 1980 AFDC [Aid to Families with Dependent Children] payments, in constant dollars, declined 56 percent," he says. "What were the effects? . . . In the large I see none . . . . This, in my view, is the final difficulty with the argument of 'Losing Ground.' The increase in dependency in the 1970s that so concerns the author, illegitimacy, single parents, took place, or rather continued taking place, while the value of welfare benefits was declining."

The senator defends the 1960s commitment to social programs as producing the "extraordinary achievement of this era -- the near abolition of poverty among the aged."

He says that "indigence all but disappeared among the aged while it significantly increased among the young," due to the government's indexing Social Security and many other "entitlement" programs, with the prominent exception of AFDC. Moynihan says that in 1983 there were 13.8 million poor children (under age 18), compared with 3.7 million poor people over age 65.