The House Ways and Means Committee voted 23 to 12 yesterday to start phasing out the Civil Service retirement system and bring 2.4 million federal employees into the Social Security system on a mandatory basis on Jan. 1, 1982.

The present Civil Service system, which requires far higher contributions but also pays much bigger benefits than Social Security, would then be restructed into a new system paying workers supplemental benefits.

The date for bringing federal workers into Social Security was put four years into the future in order to give the Civil Service Commission and the Department of Health Education and Welfare time to study ways to integrate Social Security and Civil Service retirement - and Congress time to act on "meshing" the two systems together.

The final provision also mandates federal coverage on Jan. 1, 1982 for about 4 million employees of state and local governments and nonprofit organizations who currently aren't in.

Under an amendment by Rep. Joseph L. Fisher (D-Va.), the "meshing" is intended to leave federal employees without any reduction in total protection even though it will be handled by two systems instead of one.

However, federal employee unions fear that the phasing out of the current system and putting federal employees under Social Security will end up with federal employees worse off than now and they lobbied openly at every break in committee business for softening of the terms of mandatory Social Security coverage.

An amendment by Joe D. Waggonner (D-La.) to kill the federal employee provision was rejected by the Ways and Means Committee 22 to 13 with Republicans solidly against it and Democrats split.

Fisher then moved to delay coverage tentatively scheduled for Jan. 1, 1980, under a Social Security bill drafted by a subcommittee until Jan. 1, 1984. "Let's back off a little here and find out how to do this and then proceed," he said.

However Sam Gibbons (D-Fla.) offered a substitute setting the date at Jan. 1, 1982, and it won on the 23-to 12 vote with Republicans solidly for the change in Fisher's plan and Democrats again split.

Fisher, who had backed Waggonner's original proposal to kill the coverage altogether, said the final result was better than 1980 coverage and would give the government time to study the matter before abruptly moving for coverage.

Several members of the committee said privately, however, that the delay would be used by federal employee union and opponents of universal Social Security coverage to seek ways to repeal or thwart the provision.

Social Security Commissioner Bruce Cardwell told the Ways and Means Committee that the administration preferred to wait before mandating coverage until a proposed federal commission on pension system was able to study all pension problems and report back.%TWaggonner, committee Chairman A1 Ullman (D-Ore.) and other Democrats left little doubt that there will be strenuous efforts on the floor and in the House-Senate conference on Social Security financing to strip out the new coverage date.

Inclusion of federal workers was strongly pushed by Republicans in the Social Security Subcommittee on a number of grounds. Barber Conable (R.N.Y.), William A. Steiger (R-Wis.) and others said on numerous occasions that ultimately "meshing" the systems would guarantee against "double dipping" by persons who work relatively brief periods in Social Security covered employment and then qualify for both Social Security and federal pensions.

Other Republicans said it was a matter of simple equity before the country that federal employees including members of Congress, should be covered under the same basic system as everyone else.

Inclusion of federal employees in the long-run would save money by ending double-dipping and by bringing in a well-paid group whose tax input into the system will be great, proponents said.

In the short run inclusion of federal workers and state and local government workers would pump many billions into the financially ailing system before the persons paying in would start collecting benefits. Supporters of coverage said none of the rights already earned by persons in federal employment would be lost.

Persons who have worked any time under the existing system would get full credit for their work - and the purpose of the "mesh" study is to determine how the two systems could be fitted together so that those rights would not be discarded.