The Federal Office of Child Support Enforcement received a C grade on a "report card" released Friday by a congressional panel, while the states and territories ran a gamut from A to F for programs to ensure that non-custodial parents support their children.

"The need for better child support enforcement is obvious," Rep. Thomas Downey, D-N.Y., said in releasing the 41-page report prepared by the staff of the House Ways and Means Committee. Downey is acting chairman of the subcommittee on public assistance and unemployment compensation."In the U.S. today, there are nearly 9 million mothers with children whose fathers do not live with them," Downey said. "Only about 2 million of these families received their full child support payments in 1985. Another 1 million families received partial payments, and almost 6 million received nothing. We can and should do better."

A mandatory wage withholding provision that is included in the welfare law signed by President Reagan on Thursday will help resolve the problem, Downey said.

The report card graded the Federal Office of Child Support Enforcement based on questionnaires sent to the 54 state and territorial child support enforcement programs.

It also graded each of the state and territorial programs based on questionnaireresponses and other data.

The federal OCSE received an average grade of C, but "barely missed a D," Downey said.

Wayne Stanton, administrator of the Family Support Administration, which oversees OCSE, said he was not displeased with the office's showing on the report card.

"I think in the ultimate end, this report will tend to improve child support around the nation, and that's what I care about," Stanton said.

The states' grades ranged from excellent to failing, but as Downey noted, they were marked on a curve.

"The state of Michigan is the valedictorian of the class," he said. "Three other states _ Delaware, New Jersey and North Dakota _ also earned an A."

Seven jurisdictions flunked: Mississippi, New Mexico, Oklahoma, Texas, West Virginia, the District of Columbia and Guam. However, Guam failed for lack of data, the report said.

States were graded on how they establish paternity; collect child support; operate cost-effectively; collect interstate payments; and reduce welfare costs.