The mayor announced that he will issue an executive order tomorrow incorporating stiff new requirements adopted last week by Congress that, among other things, may eliminate about the one-third of the staff of the D.C. City Council before the end of the year.

Announcement of the mayor's new order reforming the city's federally funded Comprehensive Employment and Training Act (CETA) program followed his delivery of a report last week to the U.S. Department of Labor that defended the city council's hiring and assignment of CETA workers.

By submitting the report, the mayor put himself in the position of defending a part of the city's CETA program that is largely controlled by his rival in the current mayoral campaign, Council Chairman Sterling Tucker.

The major bears overall responsibility, however, for all D.C. CETA activities.

On July 17, the Labor Department issued a report that alleged widespread abuses in the way the council hired, pays and assigns CETA workers.

It questioned the hiring of three specific employers, said many employees had been preselected by name in a way that suggested political favoritism and questioned the practice of assigning CETA workers to the staffs of council committees that are headed by elected council members.

Of the council's 143 employees, about 40 are CETA workers assigned to committee staffs.

In a letter that accompanied the city's response to the Labor Department report last week, the mayor asserted that the report's "criticisms are not valid. Our review indicates that deficincies (in the council's CETA program) were not substantial . . ."

If the Labor Department sticks by its original findings, the city may be required to repay hundreds of thousands of CETA dollars to the U.S. Treasury.

The order announced yesterday by the mayor is designed to block any future problems of the type the Labor Department report described.

"CETA funds must be used without discrimination, favouritism or political influence . . . (to hire) those who are the most disadvantaged," the mayor said, and the jobs must go primarily to District residents.

The use of the budgeted D.C. funds to pay CETA workers wages above the $10,000-a-year federal funding "must be controlled strictly," the mayor added.

And he said agencies must try hard to find regular non-CETA jobs for workers hired under the program.

The mayor said his order will carry out provisions voted by Congress last week as part of the D.C. budget for the 1979 fiscal year, which begins Oct. 1.

Those provisions, which will go into effect three months after President Carter signs the budget into law, will prevent the assignment of any CETA employe to work directly for an elected official or on the council's committee staffs. They also place limits on wages and employment tenure of CETA workers.

The mayor said efforts should be made to find other jobs for CETA employes displaced by the new rules.

"It is . . . my objective to assure the people of this city," the mayor wrote, "that the CETA program will be administered . . . to avoid further allegations of favouritism or other improper or inappropriate actions."

The council adopted its own proposed CETA rules recently but, in general, they are more liberal than those voted by Congress and invoked by the mayor.