Federal employees, including about 250,000 civil servants in the Washington area, would receive a 4.8 percent pay increase this January under an agreement reached yesterday by House and Senate negotiators. It would amount to the largest salary boost since 1981.

The agreement, approved at a late afternoon negotiating conference, also would double the next president's salary to $400,000, the first increase in the chief executive's pay since 1969. It also would clear the way for a salary hike of about $4,600 for members of Congress, who now get $136,700.

The pay and benefit packages of federal workers in the area help underpin the region's economy. Preliminary calculations showed the pay boost would amount to $2,856 for the typical white-collar government worker here, bringing the average annual salary up to $62,365.

Federal raises are decided as part of the annual appropriations process, and government-wide, the 4.8 percent raise will cost $3.84 billion, congressional aides said. But the pact does not include full funding for the added payroll expenses, which might force cash-strapped agencies to impose hiring freezes and offer early retirement incentives.

Rep. Steny H. Hoyer (D-Md.), who lobbied colleagues and the Clinton administration for the federal employee pay raise, said the increase would ensure that civil servants received the same percentage boost as that planned for the military next year and would move federal workers closer to private-sector salaries for comparable jobs.

"It's progress, and to that extent, I was very pleased to see us get closer," he said.

Pay increases for government workers and members of Congress are among the most politically sensitive topics on Capitol Hill. But little opposition arose this year, and key congressional leaders quietly moved forward on the increases over the last seven months.

The pay raise was approved by congressional negotiators resolving differences in House and Senate appropriations for the Treasury Department, White House and general government operations. The $13.7 billion conference agreement will be sent to the House and Senate floors for approval, which is expected, before going to President Clinton.

Clinton is not expected to oppose the proposed pay raise for federal workers, administration officials said, even though his budget request sent to Congress in February recommended a lesser amount -- 4.4 percent -- for civil service and military personnel.

The House and Senate negotiators did not have to vote on a congressional pay hike, formally known as a cost-of-living increase. It is scheduled to take effect unless blocked, which has not happened this year.

Congress last accepted a raise for its members in 1998, after freezing their pay in 1994. Because congressional pay sets the ceiling for federal judges and top government officials, yesterday's decision to let the 3.4 percent raise for Congress go forward will likely have a ripple effect and pull up judicial and executive salaries.

There was virtually no debate on the pay proposals yesterday, but Hoyer paid tribute to Senate Appropriations Committee Chairman Ted Stevens (R-Alaska) and members of the Washington area delegation for supporting the pay hike.

The push to give federal workers one of their biggest raises in two decades began in February when Sen. John W. Warner (R-Va.), chairman of the Senate Armed Services Committee, decided the military should receive a 4.8 percent hike as part of an overall effort in Congress to improve defense readiness and take better care of the nation's armed forces.

Within days, members of the local delegations, led by Hoyer and Sen Paul S. Sarbanes (D-Md.), began pressing for "pay parity" between the civilian and military branches. Federal employee unions launched grass-roots lobbying campaigns.

During the spring and summer, Sarbanes, Hoyer and Rep. Frank R. Wolf (R-Va.) attached pay parity amendments to at least three bills moving through Congress. In early August, Hoyer talked with Office of Management and Budget Director Jacob "Jack" Lew and won his support, aides said.

Later that month, Hoyer told House Republicans he planned to raise the parity issue during negotiations on the Treasury Department appropriations bill. Then Stevens weighed in and supported the 4.8 percent raise, aides said.

The conferees also decided to double the next president's pay, now set at $200,000, because key members thought it was long overdue -- the last Oval Office salary raises came in 1949 and 1969. The Constitution only allows presidential pay raises at the change of administrations, which means Congress can boost the president's salary in 2001 or it would have to wait until January 2005.