The number of federal workers who would be refused within-grade pay raises would nearly quadruple under a pending change in the government's pay-for-performance system.

Currently, 99 of every 100 white-collar federal workers get a within-grade pay raise each time they become eligible, through length of service, for the step increase. Depending on their time in a particular grade, workers come due for a step increase every one, two or three years. The raises are worth about 3 percent of one year's salary.

But the Office of Personnel Management estimates that under its proposed new standardized performance rating system, about 96 percent of all employes would get the raises. Under the tougher system, OPM figures that more employes would get "unsatisfactory" ratings that would take them out of the running for a within-grade raise.

At present, OPM says, about 12,500 employes (of a work force of 1.4 million) get "unsatisfactory" job ratings each year. If they are eligible for a within-grade raise but get a bad rating that year, they lose the raise.

OPM figures that under its new system--which would be phased in over a three-year period starting next year--the number of employes getting "unsatisfactory" ratings would rise to slightly more than50,000.

Federal worker unions oppose the new performance pay system. But it will go into effect next year unless Congress blocks it.