City efforts to collect child support payments have lagged because U.S. marshals have been unable to deliver court summons to absent fathers, D.C. Department of Human Resources officials said yesterday.

A blacklog of 600 to 700 undelivered notices has developed since last September, according to officials in DHR's paternity and child support enforcement office.

In order to expedite the collections effort, DHR has been authorized to have its own investigators serve notices of court action, beginning next week.

DHR director Albert P. Russo said he obtained a ruling from the Corporation Counsel's Office that there is no legal barrier to such action.

Russo said the marshals "just weren't cutting the mustard." He said four of the child support office's six investigators now will serve summons to absent parents.

J. Jerome Bullock, U.S. marshal for the District of Columbia, said his office approves of DHR taking the summons serving role. The office is understaffed and has had heavy workloads recently because of the trials of 12 Hanafi Muslims in Superior Court, Bullock said.

Bullock said the staff shortage as well as additional security and prisoner movement engendered by the murder and conspiracy trials caused his office to return 5,600 of the approximately 7,000 court papers it received for service during June.

About 80 per cent of the District of Columbia's 32,000 cases of Aid to Families with Dependent Children, (AFDC), the major federal welfare parogram, result from the absence of parents, usually fathers, who may be able to support their children, according to Russo.

Under the federal child support enforcement program, known as Title 4D, DHR began parent location and collectionattempts last year, Summonses for court action were first sought through the Corporation Counsel's office in September, 1976, DHR officials said.

The Department of Health, Education and Welfare pays 75 per cent of the program's administrative costs, and the local government 25 per cent. Half of the child support payments collected from AFDC parents goes to the local government, and the rest ot HEW.

Russo said the amount of support collected by DHR is now "slightly more" than the program's administrative costs. Earlier this year, HEW reported that the District and several other U.S. jurisdictions were collecting less in child support than the administrative expenditures.