The House will be begin debate next week on a Budget Committe proposal that would cost present and future federal retirees millions of dollars in inflation-protection cash. Both the Senate and House Budge Committees have voted to block funds to pay more than one cost-of-living raise each year for the more than two million federal and military retirees.

Federal-military retirees now get delayed cost of living adjustments, in March and September. Social Security recipients get a single cost of living raise each July.

Backers of the Budget Committee's plan to drop one of the two living cost adjustments, which go to 70,000 area people, say it will save millions of dollars and put federal retirees on the inflation-adjustment cycle as the majority of retired Americans under Social Security.

Carter administration officials once considered a similar pension cutback plan, but scrapped it in the face of Pentagon objections. The Defense establishment is wrapping up a comprehensive study of military retirement benefits, and wanted no changes made until its report is completed and studied.

However, both the Senate and House Budget Committees have approved the concept of a single cost-of-living adjustment each year for retirees. If the plan is adopted retirees would still get the September adjustment this year (they got 3.9 percent in March). But after that the next raise would not come until July, 1980.

Most of the congressional support for the twice-a-year raises comes from Washington area members, who represent more than half a million civilian and military personnel, retirees or their survivors.

Reps. Gladys N. Spellman (D-Mid.) and Herbert Harris (D-Va.) both are on the Post Office-Civil Service Committee. It has jurisdiction over federal retirement matters, and Spellman and Harris can be expected to try to block the plan to eliminate one of the retiree raises. The Budget Committee has authority to force the Civil Service unit to report out the legislation, although it is not likely to pull its legislative rank on this issue.

When budget amendments come up Tuesday or Wednesday, Rep. Joseph L. Fisher (D.Va.) will proposed that the spending cuts the Budget Committee approved, cuts tht would eliminate one of the raises, be rescinded.

To build support for his case, Fisher has sent a "Dear Colleague" letter to each House member, explaining the Budget Committee action, and recent "deliberalizations," of the federal retirement program.

Retired members of Congress also get the twice-yearly living cost raises.

"If this reduction is approved," Fisher wrote, "it will be the second cut in three years in the retirement benefits for these [federal and miliary] groups. In 1976 the system was changed to calculate the increases semiannually and repeal the 1 percent that was added each time to compensate for delayed raises."

When Congress eliminated the 1 percent add-on in favor of two flat annual raises, Fisher said, the plan was "praised as an improvement and as an offset to the benefit reduction. It is unfair to propose another change so soon. Retirees should know what their benefits are and not have them constantly changed and reduced.