Private-sector workers are earning salaries and benefits worth 7.2 percent more than those offered comparable federal government workers, according to a report issued yesterday by the House Post Office-Civil Service Committee.

The data, assembled by the Hay Group, a management consulting firm that specializes in benefits analysis and actuarial services, shows that federal salaries are 10.3 percent smaller than those for similar jobs in the private sector, while federal retirement and leave benefits are worth about 7 percent more than those in industry.

The report comes just as the Reagan administration is putting the final touches on a budget plan that is expected to freeze federal pay and propose significant cutbacks in federal retirement benefits next year.

Earlier this year President Reagan rejected a report by government pay experts calling for a federal pay raise of nearly 18 percent that would allow salaries to catch up with industry. Instead he ordered that a 3 1/2 percent raise go into effect next month.

Prepared for the Hay Group by Edwin Hustead, former chief actuary of the Office of Personnel Management, the report matched salaries, vacations, holidays and pension benefits offered employes in 1,200 large and midsize firms, ranging from nationwide giants such as IBM, General Electric and GTE, to local firms such as Government Employees Insurance Co.

The consultant concluded that government health care benefits trail the private sector by 2.2 percent; disability benefits by 0.7 percent and death benefits by 0.7 percent. Another finding was that special benefits offered some private-sector executives, such as stock options and company cars, are worth an additional 1.2 percent.

Rep. William D. Ford (D-Mich.), who chairs the House committee, said of the report: "Any fair-minded person would have to agree that federal employes have fallen behind their private-sector counterparts in total pay and benefits."

The committee, dominated by Democrats, acts as the primary channel for legislation affecting the government's 1.8 million workers. In the past three years it has successfully blocked many legislative attempts by the Reagan administration to change federal pay and fringe benefits.

Under the federal pay law, government workers are supposed to get raises each year to keep their pay comparable with the going rate for similar jobs in the private sector. That annual salary survey is made by the Bureau of Labor Statistics and covers only wages.

Presidents Ford, Carter and Reagan all asked Congress to adopt a system that would expand the pay survey to include wages of the nation's 12 million state and local government employes and compare the total value of fringe benefits offered.

Each president thought that the so-called total compensation approach would narrow the gap between government and industry. But Congress rejected that approach, under pressure from federal employe unions that believed it would make government employment appear overly generous.

Data from the new report, however, indicates that comparing total compensation could result in larger pay recommendations for U.S. workers and justify improving, rather than cutting, some benefits.

The average salary for federal workers in the Washington area is $30,784, according to the OPM. The median federal salary here is $27,252. Both figures are higher than those for the typical non-federal American workers.

But federal worker groups argue that the U.S. government needs more highly trained professionals and specialists than most private firms.