A landmark court ruling giving women who work for Washington state substantial pay raises was overturned on appeal today, dealing a severe blow to efforts by unions and feminist groups to make "comparable worth" the law of the land.

A three-judge panel of the 9th U.S. Circuit Court of Appeals in San Francisco ruled that the 1964 Civil Rights Act "does not obligate [Washington state] to eliminate an economic inequality which it did not create."

Comparable worth, the principle of equal pay for different jobs that require the same amount of preparation and responsibility, has become one of the key feminist issues of the 1980s. U.S. District Court Judge Jack Tanner's 1983 decision ordering comparable pay for state government secretaries and truck drivers in Washington state has been followed by comparable worth studies in many other states and new union agreements based on the principle in major cities such as Los Angeles.

Tanner's decision could have provided as much as $1 billion in damages to 15,500 state workers for failure to implement a 1974 comparable worth plan. Some political leaders, including San Francisco Mayor Dianne Feinstein, have resisted comparable worth plans for fear the salary increases would create budget deficits.

Washington state Attorney General Ken Eikenberry said tonight, "I'm delighted with the result."

He said he had assured the state Legislature that the Tanner decision would be overturned and remained confident that the Supreme Court would reject any appeal of today's ruling.

The Reagan administration has consistently opposed comparable worth proposals. The president was quoted this summer as calling the idea "cockamamie," and earlier in the year U.S. Civil Rights Commission Chairman Clarence M. Pendleton Jr. said it was "probably the looniest idea since 'Looney Tunes' came on the screen."

Eleanor Smeal, president of the National Organization for Women, said tonight that the setback shows the need "to fight sex discrimination on several fronts at the same time." She noted that NOW and its allies had persuaded the Washington state Legislature to appropriate $42 million to help narrow some wage gaps while waiting for the appeals court decision.

Critics of comparable worth have expressed the fear that the principle might eventually be forced on private businesses and require salaries based on "comparable worth" calculations by personnel consultants rather than supply and demand. Judge Anthony Kennedy, writing for the three-judge panel in today's decision, appeared to agree with the critics. "Neither law nor logic deems the free market a suspect enterprise," he said.

In his 1983 ruling, Tanner had cited a study commissioned by the state government showing a 20 percent salary gap between workers in predominantly female and predominantly male jobs that involved similar skills, intelligence, responsibility and working conditions.

Kennedy, in language certain to be cited by comparable worth critics battling in courts and legislatures across the country, said the wage gap by itself did not prove that the state intentionally discriminated against women.

He said the court had decided that even a public employer such as Washington state can follow prevailing private market wages in setting salaries, whether this underpays workers in jobs held predominantly by females or not. "The state did not create the market disparity and has not been shown to have been motivated by impermissible sex-based considerations in setting salaries," Kennedy said.

There was no dissent filed with the Kennedy opinion.

Feminist groups have argued that comparable worth is one important way to cure the ills of decades of discrimination in which women were deliberately shunted to low-paying clerical jobs and not allowed to apply for higher paying jobs as technicians and drivers. The American Federation of State, County and Municipal Employees filed the court case in Washington state, as well as cases in other states such as California, where 100,000 past and present state workers could be affected.

The union had sued Washington state for immediate implementation of comparable worth, and back pay for previous inequities, after the Legislature passed a bill calling for narrow wage gaps over a 10-year period.

Union attorney Winn Newman argued that the state's study showing a wage gap obliged it to act immediately under federal civil rights law. But today's decision said, "a study which indicates a particular wage structure might be more equitable should not categorically bind the employer who commissioned it."

Newman said that "we are quite surprised and shocked" by the decision, and that they expect to make some kind of appeal.

The value of a job to an employer "is but one factor influencing the rate of compensation," Kennedy said. He said the state could also consider whether workers in certain categories are hard to find and evaluate the effectiveness of collective bargaining.

The union may ask the appeals court to call an 11-judge panel to reconsider the decision or appeal to the Supreme Court. Eikenberry said he doubted that the current high court would agree to hear the case.