A state Senate committee unanimously approved legislation yesterday that is designed to make it easier for persons who are owed child support or alimony to obtain liens against their spouses' wages for such payments.

The measure approved by the Judicial Proceedings Committee now moves to the 47-member Senate, which last year passed legislation virtually identical to the current proposal.

The bill, which would activate liens against persons' earnings if they fall 30 days behind in court-ordered child support or alimony, would establish "a single-purpose, efficient system" of collection, declared Ann C. Helton, executive director of the state Child Support Enforcement Administration, which helped draft the bill.

About 80 percent of the more than 125,000 child-support cases in Maryland are more than 60 days in arrears in payments, according to state officials, who said those outstanding payments total $350 million.

Maryland law now allows courts to attach a person's wages and withhold child support, but critics have argued that the current system is too complex and time-consuming to be effective.

By triggering automatic liens after 30 days of delinquency, the proposal would improve enforcement of current child support laws and reduce the burden on courts and state agencies, supporters said.

Committee Chairman Thomas V. Mike Miller (D-Prince George's) said the state stands to lose millions of dollars of federal welfare aid if the General Assembly does not approve the legislation this year.

Maryland must conform with a national child-support enforcement law signed by President Reagan last year to receive more than $100 million in federal aid to families, Miller added.

Pressure to conform with the federal law should "positively, unequivocally" ensure passage of the bill by the Judiciary Committee and full House of Delegates, Miller said.