Rep-Charles C. Diggs Jr. (D-Mich.), convicted of illegal payroll kickbacks said yesterday he will relinquish his committee chairmanships and his right to vote in the House for the rest of this congress, but, if reelected, he expects to reassume his chairmanships and start voting again.

Diggs made the announcement in a letter to Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.). In it he said he would "voluntarily comply" with House Rule 43, which says a member of the House convicted of a crime of which a sentence of two or more years in prison may be imposed "should refrain" from voting or participating in committee work until he is officially cleared or reelected.

Diggs was convicted Saturday on 29 counts of mail fraud and illegally diverting more than $60,000 of his congressional employes' salaries to pay his personal bills. He faces imprisonment of up to five years on each count. No date for sentencing has been set and Diggs has said he will appeal.

Diggs said he would comply with the rule although it is "not binding" but he added that he is up for reelection and "if reelected, will resume, pursuant to the rule, my normal responsibilites and activities in the House and on both the House Committee on the District of Columbia and International Relations."

Since the House is expected to adjourn this weekend, Diggs would only sit out for three or four days.

Diggs chairs the District Committee and is chairman of the International Relations subcommittee on Africa.

Diggs, the senior black in the House, is a heavy favorite to be reelected to a 13th term. Yesterday he rejected a Detroit Free Press editorial suggesting he resign.

"I will be guided by the wishes of my constituency," he said at a press conference in Detroit.

If Diggs is reelected, his intention to resume his activities could pose a dilemma for House Democrats, particularly the leadership.

It is the leadership's committee, the Steering and Policy Committee, which nominates Democrats for committee chairmanships. The committee would have to decide whether to renominate Diggs for the District Committee chairmanship. He also would have to stand for election by all House Democrats in the Democratic Caucus. In recent years the reform-minded caucus has stripped three members of committee chairmanships, largely because they were simply arbituary and capricious and out of step with the majority.

If Diggs survives those tests, he also would have to have his committee chairmanship ratified by the House. The subcommittee chairmanship would be dealt with the International Relations Committee.

However, the caucus and/or the House could vote to take any number of other steps against Diggs, from a reprimand or censure to a fine or explusion. However, expulsion would require a two-thirds vote, and no member has been expelled for corruption.

As a result of the Adam Clayton Powell case in the 1960s, however, it seems clear the House cannot refuse to seat Diggs, even though he has been convicted of a crime. The Supreme Court ruled in 1969 that the House cannot go beyond the qualifications set by the Constitution in seating members. The Constitution lists only age, residency and citizenship as requirements for House membership.

If Diggs is reelected and imprisoned he would not be the first House member to serve from jail. At least one, Thomas Lane of Massachusetts, was jailed for misuse of funds, and even campaigned from jail.

Before the House goes home this weekend, it must act on reprimand and censure recommendations voted by its ethics committee against three members involved in the South Korean influence-buying scandal.

The committee recommended censure for Rep. Edward Roybal and reprimands for Reps. John J. McFall and Charles H. Wilson, all California Democrats. McFall is charged with failing to report a campaign contribution and Roybal and Wilson with making false statements about money they received from Korean businessman Tongsun Park. Only the action against Roybal is expected to generate a fight, since Hispanic groups think he is being made to bear the brunt of the punishment unfairly.

If McFall is reprimanded, his position as chairman of the Appropriations transportation subcommittee may be in jeopardy.