RICHMOND, DEC. 16 -- A federal judge has removed a ban on regulations that reduce the amount of welfare a family receives if members of the family receive Social Security or child support payments.

On Tuesday, U.S. District Judge Richard L. Williams lifted his 18-month ban that had protected Virginia welfare families from the impact of federal cost-cutting measures.

Most of Virginia's 58,000 to 60,000 welfare families are not affected by Williams' ruling, officials said. But families with children receiving Social Security payments because of a dead or disabled parent, or child support payments from a divorced or separated parent will now have those payments subtracted from their welfare benefits.

In June 1986, Williams temporarily blocked the congressional measure from taking effect in Virginia. His ruling Tuesday was based in part on a recent Supreme Court ruling that approved requiring children with child support to be counted as family members in determining welfare benefits under Aid to Families with Dependent Children.

The ruling meant the family is considered larger and thus so are welfare benefits. But because child support payments often are greater than welfare payments, it often means an overall loss for the family when the outside payments are subtracted from welfare.

Williams' order applied the principle of the Supreme Court decision to Social Security benefits as well as child support.

Jamie B. Alipertie, a legal aid lawyer representing the welfare children, said the basis of Social Security benefits has always been "that they be used only on behalf of the beneficiary," and said that will be changed by the new regulations.

Assistant U.S. Attorney Robert W. Jaspen said the Supreme Court approved using outside support for other members of the family because it typically benefits each member.

Williams' order, likely to be issued this week, will lift his ban on regulations pertaining to both types of benefits.

Williams also ruled that the federal $50 exemption, or "disregard," which families are allowed to keep from child support without being figured into their welfare payments, also applies to Social Security support.

Lawyers for the welfare children and for the federal and state governments said they did not know whether they would appeal.