Thousands of delinquent parents are expected to receive bad tidings in a Christmas card this week from the District government. "Happy Holidays," says the card, bearing a smiling picture of Santa on the front. "You have not paid your child support!"

The cards are part of what Mayor Marion Barry yesterday announced is an aggressive program to improve the District's poor performance in collecting child support payments. The mayor said the city plans to collect millions of dollars in delinquent payments, in part by deducting support payments from city employes' wages and city residents' income tax refunds.

Barry, noting that the U.S. Marshals Service has 4,000 outstanding warrants for parents who are delinquent in child payments, said the city has established a grace period during which parents can make payments without fear of arrest.

Barry's announcement of the grace period at a news conference yesterday came nine days after the period began. It is scheduled to run from Dec. 14 through Jan. 15, he said.

In a report to Congress, the U.S. Department of Health and Human Services found that the District ranked last nationwide in a comparison of payments collected and administrative expenses during fiscal 1986. The District collected 92 cents in child support for every dollar spent on the city government's administrative costs.

Barry, acknowledging that the city's program has been ineffective, said he plans to improve the national ranking by taking "creative steps," including booting cars if necessary, to raise the city's overall collection efforts from $7 million collected in fiscal 1987 to $15 million during the current fiscal year.

"These children are going to get their money," Barry said.

The D.C. Department of Human Services has 57,000 cases in which child support has been requested, the majority of which have not been processed to the point of obtaining court orders for payment. City officials estimated that the 4,000 cases in which there are outstanding warrants represent $14 million in overdue payments.

Barry said he plans soon to hire a new Office of Paternity and Child Support Enforcements director who has extensive experience in turning around troubled systems. In addition to deducting payments from wages and income tax refunds, Barry said, the new director will have the authority to place liens against real and personal property and release information to credit bureaus on people who owe more than $1,000 in support payments.

The HHS report to Congress found that the District in fiscal 1986 collected payments in 3,183 cases out of an average annual caseload of 53,125. The average annual caseload includes petitions for payment that have been processed by the District and have resulted in court orders for payments, as well as pending petitions.

An HHS spokesman said the District was warned in September that the city's failure to comply with several federal standards for collecting child support could cost the city nearly $400,000 annually in federal reimbursements for public assistance payments.

As a result of the District's new plan to increase its collection levels, HHS has agreed to suspend any penalties until the District's system is reviewed again in January.

Observers who have followed the city's efforts to collect support payments had mixed reviews of Barry's new plan.

"I still worry that this is just going to be a flash and a dramatic gesture and the problem will continue," said Aileen A. Johnson, a Women's Legal Defense Fund staff attorney. "There has been a lack of commitment, leadership and performance standards on the part of the city."

Ron Henry, a lawyer who has reviewed the city's collection policy, said the changes are often unfair to men -- who compose the vast majority of the delinquents.

Henry said the system rarely considers a parent's ability to pay child support before enforcing automatic collections. He also said that the lack of an accounting system means parents have no guarantee that the child support payments are used for the children rather than a former spouse's personal needs.