Federal workers could end up paying indirectly if Congress decides to make Jan. 15 -- the birthday of the late Martin Luther King Jr. -- a national holiday.

The House, so far, has rejected a single-purpose bill to create the new holiday in all 50 states. Backers say the slain civil rights leader was one of the greatest, most admired Americans.

Opponents of the measure -- walking the always dangerous tightrope of being called racists -- have proposed that Jan. 15 be made a special national observance or that it be celebrated on a weekend. They argue that only one American -- George Washington -- is so honored, and/or that additional holidays cost government and business billions of dollars. (Each federal holiday "costs" Uncle Sam $25.2 million in wages in metro Washington, in addition to premium pay required for workers who must be on duty, holiday or not.)

Even if the current bill in Congress fails, the issue of Martin Luther King Jr.'s birthday will come up again, with White House backing.

Tucked away in President Carter's civil service pay reform legislation -- which Congress will work on next year -- is language that would make Jan. 15 a holiday for most federal workers.

Ironically, the extra day off could wind up costing federal workers in the form of smaller future pay raises.

Carter's bill would give the president greater leeway to set federal pay raises each October. It proposes to link government salaries to the going rate for similar jobs in private industry, and to further refine federal pay scales to make them conform to private industry pay rates.

One feature of the pay "reform" most opposed by federal union leaders is the "total compensation" concept. Compensation covers a lot more than pay. i

For example, under the Carter plan, federal fringe benefits (retirement, insurance, vacation, and holidays) would be compared with those in the private sector. Although you can get an argument of the subject, most impartial observers agree that in terms of retirement, vacation and holidays, federal workers are better off than their industry counterparts. So, adding another holday could be costly.

Government workers already get nine holidays. They are: New Year's Day Washington's Birthday Memorial Day Independence Day Labor Day Veterans Day Columbus Day Thanksgiving Day Christmas

Washington area civil servants receive a bonus holiday -- Inauguration Day -- every four years.

In addition federal workers frequently get extra time off before Christmas or New Year, if either of those days fall on a Tuesday or Thursday. President Nixon gave federal employees two of the bonus holidays and this year, Carter has announced that Monday, Dec. 24, will be a holiday for federal (but not postal) employees.

In the past, those holidays have been given for patriotic or political reasons without consideration of their value as part of a federal labor-management contract or negotiation.

In the private sector, workers often have to forego part of a pay raise to get a holiday. It is true that some industrial-type employes receive their birthdays off -- in return for pay tradeoffs. But it is hard to find a private industry employe who gets as many holidays as federal workers. If you doubt it, look at the people in stores and service organizations on duty next time you visit a Washington's Birthday or Columbus Day sale.

The value of the new proposed holiday -- which is in the federal pay reform bill -- would be added to the civil service pay-fringe package when it is weighed against similar benefits in private industry.

One way to make Jan. 15 a holiday -- without adding to the number of holidays -- would be to take away one of the current nine.

Local leaders of the Southern Christian Leadership Conference last Thursday issued a call for Americans to stay away from work on Jan. 15. The idea is to show they want the day made an official holiday. Local SCLC officials were quoted as saying they did not object to making King's birthday a paid federal holiday since there are "some trival" holidays federal workers are already paid for. There is now talk of substituting King's birthday for another holiday, if the sole congressional objection to the new holiday is on the grounds of cost. Next question: Which holiday do they cut?