Rep. Herbert E. Harris (D-Va.) will mount a salary battle in behalf of federal employes today against President Carter's proposal to hold pay increases for federal and military workers to an average of 5.5 percent.

Harris said he would introduce a resulution of disapproval in the House. If the resolution is supported by a majority, it would order an 8.4 percent increases on Oct. 1. The president's pay advisers have said this amount would be necessary for government workers to catch up with salaries in comparable jobs in private industry.

A similar action in the Senate also would trigger an 8.4 percent increase, bu there has been no indication of any such action in the upper house.

Harris admits the chances of Congress overriding the president one month before voters go to the polls across the nation is unlikely. But because federal workers make up a large part of his constituency, Harris is going to make the effort in their behalf.

In a year when inflation is the number one political issue, it's not even certain Harris will have the support of other area representatives, even though they also have a large number of federal workers in their districts.

Rep. Gladys Noon Spellman (D-Md.) who cosigned a letter with Harris on April 29 urging their House colleagues to oppose any effort to place a cap on pay increases, will not cosponsor Harris' resolution today, according to a spokesman.

Spellman "will support the resolution if it gets to the floor," the spokesman said.

Harris plans to introduce the resolution as a preferential motion, meaning that if, as expected, it fails to get the support of the House Post Office and Civil Service Committee to which it will be referred, it still can be brought before the full House for a vote.

Three years ago, when President Ford similarly placed a cap on federal pay increases, Harris unsuccessfully sought to get the House to overturn the presidential action.

If Congress does not override the president's decision, announced last week, the smaller pay increases automatically will take effect next month.

The president said that under normal circumstances he would not hesitate to order the larger increases. But he added that the government must "set an example" for private industry to hold the line on wages and prices and to stop the "treadmill" of inflation.

Harris said Ford's action in placing a cap on federal salaries "didn't act as an example" to the private sector in 1975, and Carter's intention to do the same thing "certainly didn't either."

The comparability pay plan, instituted in 1971, was not meant to provide federal workers with cost-of-living increases, Harris said, but to allow them to catch up with workers who hold similar jobs in private firms. As a result, Harris said, the recommended increases "always runs a year to 18 months behind" what those private workers already are receiving.