Seventy temporary D.C. government workers who were to collect fallen leaves in Washington's neighborhoods for the next three weeks lost their jobs yesterday as the city's Department of Environmental Services began cutbacks aimed at helping the District avert a projected $110 million budget deficit.

Environmental Services, which hired the 70 workers on Oct. 1 and had planned to keep them on the payroll for a total of 10 weeks, is apparently the first city agency to terminate temporary workers as an economy measure. Temporary workers can be terminated at any time because they do not have the same job protections as permanent employes.

Mayor Marion Barry has repeatedly promised there would be no layoffs of city workers. In Los Angeles, where he is attending a National League of Cities conference, Barry said Monday that his promise covered only permanent, full-time workers.

An official in the city's personnel office said yesterday that no general directive had been issued to lay off temporary workers.

"If we had kept these temporaries on for the full 10 weeks we would have been overspending," said William B. Johnson, director of the Department of Environmental Services. "Things are too tight to be overspending."

The city's budget office, which forecast the deficit, has given all departments new, lower budget ceilings, although the District is only two months into the new fiscal year. Each department must now tell the budget office how it intends to stay within the new limits.

In January, the mayor, with recommendations from the budget office, will determine finally how to balance the city's books, said budget director Gladys W. Mack.

Johnson said that to make up for the work that the temporary workers would have done, the city's street cleaners will suspend their regular work for the next three weeks and instead gather leaves.

The 70 workers were notified the day before Thanksgiving that their jobs would end Dec. 1, Johnson said. An undetermined number of other temporary workers at DES will retain their jobs, he said, because they are paid from federal grant funds that are not subject to city cutbacks.