Federal managers and supervisors -- including 30,000 Grade 13, 14 and 15 people here -- will get an automatic pay raise of at least 4.8 percent next month, double the amount they had been slated to receive under a controversial pay-for-performance system that was due to begin Oct. 1.

The Office of Personnel Management, which had hoped to have the carrot-and-stick merit pay system for 125,000 mid-level officials functioning next month, says it reluctantly will delay implementation of the program that would have limited supervisors-managers to one half of the regular October federal pay raise, with additional increases coming later based on merit.

OPM's decision to delay the merit part of merit pay, a cornerstone of former President Carter's civil service reform package, means that virtually all of the supervisors-managers -- who were due automatic raises of only 2.4 percent -- will get at least the same 4.8 percent that goes to their subordinates. Individuals under merit pay who are rated at or above the "fully satisfactory" or "fully successful" level by their bosses will get additional, unspecified, percentage increases.

OPM officials, who were anxious to have the merit pay system running this year, bowed to pressure from the General Accounting Office. It just completed a report (B-203022) saying the merit system could fall on its face this year because it needs more work. When Congress passed the Civil Service Reform Act more than two years ago it said that most federal agencies were to have merit pay systems for their supervisors and managers in effect by October 1981. However, delays in setting up rating systems, confusion over how much more outstanding personnel should get, and pressure from the Federal Managers Association and other groups caused enough second-thoughts to have the program put on hold for another year.

OPM chief Donald J. Devine, clearly ticked off at the last-minute GAO ruling (which he called "ill-timed"), said he remains committed to merit pay but cannot now implement its most important feature -- performance pay. It means everybody under merit pay who was supposed to get an initial raise of only 2.4 percent this October now will get 4.8 percent with more to come for some. They will get the raise at the same time as the government's million-plus rank-and-file white-collar workers.

Devine said some workers with top ratings under merit pay will get larger increases from their agencies, but those raises will be smaller than the 10- to 12-percent raises they could have expected if merit pay had come into effect on schedule.

GAO advised the personnel agency Tuesday that the method for calculating merit pay didn't meet congressional requirements and said OPM should forget about putting merit pay into effect this October. Devine feels that the merit pay plan should have been put into effect this year, but the fact that GAO's ruling comes "only three weeks prior to the date on which we are required by law to implement the merit pay system leave me no choice," but to stick with the present system and give merit pay people the same raise as other workers.

Under merit pay, designated personnel in GS 13 through 15 ($32,048 to $50,112.50) no longer get automatic time-in-grade raises (worth about 3 percent) that regularly go to most other workers. Those increases come every 1, 2 or 3 years depending on an employes' time in grade. Money saved by denying those and other automatic increases to supervisors and by giving merit pay people only half the regular October increase is to be used to finance performance raises (the best people getting the most) for those in the merit pool. The system will go into effect next year unless Congress decides to kill it and keep everybody in government (but top executives) riding on the same automatic pay cycle.