Plans to delay a controversial change in the federal government's seniority-based pay and layoff system were overriden yesterday by the White House's Office of Management and Budget, which said the policy will go into effect as scheduled next Monday.

Yesterday's action means that a new performance-based system -- making step increases harder to come by and weakening the job security of longtime employes when there are reductions in force -- will become effective when a congressional ban on the changes expires this weekend. The Office of Personnel Management had planned to delay implementing the rules change, which already has been blocked twice by Congress.

The policy change will affect the way longevity pay raises and reductions in force are handled for all of the nation's 1.2 million white-collar civil servants, about 360,000 of whom live in the Washington-Baltimore region.

The Office of Personnel Management submitted a regulatory proposal to OMB Tuesday because it needed the approval of its more powerful sister agency before the delay could be formally announced in the Federal Register.

Personnel agency officials thought they had reached a compromise with congressional Republicans and Democrats that would have given both sides more time to work out new performance-based job rules.

Management and Budget spokesman Edwin L. Dale Jr. said yesterday that the proposal was rejected because changing pay and layoff rules is part of administration policy.

Late yesterday OPM officials said the status of the rules was still being discussed. But Dale said his agency had been informed earlier in the day that the proposed delay was rejected.

OPM could appeal to the White House, however. A congressional staffer who asked not to be identified said that OPM had asked Republicans on the hill to send an "emergency letter" to Budget Director David Stockman asking him to step in and uphold OPM's request.

"This appears to be a major case of ruffled political feathers," a federal official said yesterday. "Apparently some people in the administration, and some Republicans . . . were upset by Wednesday's Washington Post story about the plans to delay because it used the word 'negotiation' rather than 'consultation,' and because no Republicans were listed as being part of the consultation."

Sen. Ted Stevens (R-Alaska) and Virginia Republicans Stan Parris and Frank Wolf had been working with OPM on the rules change, but Maryland Democrat Steny Hoyer was credited by sources as having negotiated the delay in plans.

If the policy goes into effect Monday it means thousands of federal workers who expected to get step pay increases next year may lose out because of the new emphasis on performance ratings.

Employes are eligible for the raises of approximately 3 percent every 12 to 36 months based on a "satisfactory" performance rating. Several hundred thousand become eligible for the raises each year.

OPM estimates that under the current system, 99 percent of all who are eligible get the raises. With the new emphasis on performance standards, OPM estimates that about 96 percent will.

The major oppostion to the rules change comes from workers, their unions and members of Congress concerned about the impact during layoffs, or RIFs.

In the first three years of the Reagan administration, 2,900 U.S. workers here lost their jobs under the last-hired, first-fired guidelines. The change due Monday gives added seniority credit to employes based on their last three performance ratings.

There is a good chance, however, that new federal pay and layoff rules may be blocked by Congress again. The vehicle for doing so is a supplemental appropriation package now working its way through the Senate and the House.

The House version of the supplemental contains an amendment added by Hoyer that would delay the rules change until the start of the fiscal year in October. Congress has used that system before to block the administration.

The supplemental appropriation package before the Senate does not ban any government work rules changes, but the versions of spending bills to be approved by the Senate and House will go to a conference committee shortly. It will be charged with working out a compromise both sides can live with.

Administration insiders say that although the administration opposes the Hoyer amendment, the president would not veto any compromise supplemental appropriation bill just to kill the Hoyer proposal.

Under the new system it is possible that newer workers with top performance ratings could keep their jobs, while longtime employes with poorer ratings could be fired.