Forty members of the House, saying they were "disturbed by the increasing number of proposals for the resumption of the military draft," yesterday asked President Carter to oppose conscription as well as a return to selective service registration.

In their letter to the president, the 35 Democrats and five Republicans also urged him to reject proposals for nonmilitary national service, a concept contained in a bill submitted this year.

Rep. John F. Seiberling (D-Ohio), leader of the antidraft move, said at a press conference that forces backing a return to the draft were "coming on little cat's feet" in an attempt to "slip one over on us before anyone knows what's happening."

President Carter has said that he opposes resumption of the draft at this time, but he has left the door open to a change of view, indicating the matter would be kept under study. Conscription was replaced in 1973 by an all-volunteer force.

The Defense Department said in a major study released in December that the volunteer system has provided the military with "a full strenghth active force of a quality equal to or superior to that achieved under the draft," and it added that the study did not support drafting either for the active services or the reserves.

Since then, however, dissension has arisen between Army Secretary Clifford C. Alexander Jr. and Army Chief of Staff Gen. Bernard W. Rogers, with Alexander saying no draft is needed and Rogers insisting that a limited draft is required to fill the ranks of the ready reserves.

Seiberling yesterday called proposals to make up the gap through conscription an "unmitigated disaster." Rep. Ron Paul (R-Tex.) said the draft was a "waste of money" and "a form of slavery."

Rep. M. Robert Carr (D-Mich.), a member of the House Armed Services Committee, said "there's been no showing of evidence [before the committee] that there's a need for this . . . [the military] doesn't like this idea of going on TV and selling recruitment the way you sell automobiles."

A spokesman for a new group called the Committee Against Registration and the Draft said a small demonstration is planned at the Capitol April 30, when Congress returns from its Easter recess.

Congressional sources say chances of resurrecting the draft in this session are not good. However, House liberals are prepared for a tougher fight against bringing back selective service registration. Critics say registration could be used as a prelude to moving to a full-scale draft later.

Rep. Jim Weaver (D-Ore.), a leader of the antidraft move, predicted that a mandatory registration bill will go to the full House this year.

Rep. Paul N. McCloskey Jr. (R-Calif.) has introduced an even more far-reaching bill that would require universal service of all young Americans-either in the active army, the reserves or nonuniformed national service.

There has been no action in the Senate so far, but Sen. Sam Nunn (D-Ga), chairman of the Armed Services Committee's manpower subcommittee, has said he is for a registration requirement. He says he is not for the draft at this time and maintains registration may stimulate more interest in enlistment for the voluntary force.

Civilian officials at the Pentagon do not dispute Army figures indicating that the ready reserves, now numbering 182,000 are under strength. The ready reserves are the manpower pool available in wartime to replace combat losses and fill out the ranks of active units.

The Army says its ready reserves should be beefed up to 729,000, but the civilian side of the Pentagon says 350,000 is adequate and can be reached through a more aggressive voluntary recruitment effort.

The disagreement hinges on how quickly after war's outbreak a selective service system could start turning out replacements-and on whether the kind of war the country is likely to be fighting would require a massive pool of manpower.

Pentagon civilian officials say that within 100 days after mobilization newly trained draftees would begin to replace combat losses. They say that is time enough under the wartime conditions the nation would be likely to face.

To increase the pool of ready reservists, the Army on April 1 began accepting enlistments into the reserves for six months. The normal active duty tour is three years. If the experiment is successful, it could become a regular feature of meeting recruitment needs without resorting to a draft, Pentagon officials said.