Director William H. Webster says he would have a tough time getting and keeping the best people for the FBI if President Carter's federal pay reform plan becomes law.

Webster made his views known in a letter to Rep. Gladys N. Spellman (D-Md.). Spellman heads the House Compensation subcommittee that is considering pay reform. Webster's comments will not make the president happy. But they may bolster the antireform underground in government.

Carter's plan would set federal wages on a community-by-community basis; link them to pay and fringes of local industry and city-state governments. It would give the president sweeping new powers to determine what fringe benefits would be used in the compensation comparisons, and how much they would be worth. Congress would become even more of a rubber-stamp operation in setting federal salaries.

Federal-military personnel technically are due an October catchup-with-industry raise of about 12 percent. But if Congress okayed the president's plans by mid-summer, new measurement techniques would shave that raise to 6 percent or less. Government union leaders say the Carter plan would cost the typical civil servant $1,200 to $1,500 in raises each year.

Unions, professional groups and many members of Congress (virtually all Democrats) oppose the president's "reform." The politicians say it would cut back payrolls in their areas. Unions say the proposed payfixing changes are designed to give Carter an added hammerlock on the career civil service, giving him almost supreme authority to set the rules on wage gains. He already has greater control over hiring, firing and job classifications under his recently approved Civil Service Reform Act.

Spellman represents as many federal workers as any member of Congress. She has been skeptical of the Carter plan, and afraid it, along with new presidential powers under civil service "reform" will give the White House too much control over career workers.

Webster's comments about pay reform, while measured and mild, will not help the administration sell its proposal.Many top federal officials oppose pay reform in private, but far to speak out. Some have indicated, however, that if called to testify before Congress under oath they would spell out their misgivings.

Webster says the "potential for fluctuation fof employe benefits as suggested by the concept of 'total comparability' could present a challenge to the ability of an organization such as the FBI to effectively recruit the highest qualified candidates . . ."

Adjusting federal pay on a local basis, Webster said, "would certainly require revamping of much of our existing personnel system and will have the inevitable effect of making the compensation process more complex, since a variety of bases would have to be taken into consideration. Likewise, any number of administrative decisions, now evaluated and implemented on a national basis, would have to be independently assessed by pay region, or locality, thus complicating a number of administrative processes . . ."

Webster had other criticisms of the pay reforms proposed, mostly -- although he put it much more diplomatically -- on grounds they would screw up a system that works, increase paperwork and increase the opportunities for pay inequities -- and push good people out of the FBI. Webster probably reflects the views of a lot of top federal managers who believe pay reform is great, wonderful and overdue -- but not for their people. b