House Democrats, meeting in closed session, took steps yesterday that could strip convicted Rep. Charles C. Diggs Jr. (D-Mich.) of his chairmanship of the African affairs subcommittee.

But in a series of votes, the Democrats rejected stronger moves that would have prevented convicted or indicted chairmen of committees or sub-committees from keeping their posts.

The action that could knock Diggs out of his African affairs slot came when the Democrats decided to require the caucus to decide whether convicted or censured subcommittee chairmen should be allowed to keep their post. Subcommittee chairmen, except on the Appropriations Committee, are now elected by committee members.

But the Democrats decided not to require the same caucus vote for re-primanded members, a move that could allow Reps. Edward Roybal and Charles Wilson. Californians reprimanded in the Korean influence-buying scandal, to hold onto their subcommittee chairmanships.

Common Cause Vice President Fred Wertheimer called the caucus action an "absolute abdication of responsibility" for the transgressions of its members in the Korean case. "It's a terrible signal." Wertheimer said, adding that it "undermined" the effect of the ethics code adopted by Congress last year.

It was a real step backward. The Democratic Party and Congress are off to a bad start. This is the sort of thing that makes the American people mistrust us," said Rep. Peter Kostmayer (D.Pa.), an author of several of the defeated ethics proposals.

"I think the most disturbing thing was that the acucus was closed to the press and public. It was a bad day for reformers," Kostmayer added.

However, most of the "reformers" led the move to close the acucus, including Speaker Thomas P.O'Neill Jr. (D.Mass), who last year pushed for the new ethics code, Rep.Phillip Burton (D-Calif.) and Rep. Abner Mikva (D.III), head of the "reform-minded" Democratic Study Group.

The proposals would have affected four members of the House who have been convicted or indicted in court or reprimanded by the House for their part in the Korean scandal.

Diggs has been convicted and sentenced to three years in prison for taking salary kickbacks from his staff. He voluntarily gave up the chairmanship of the District of Columbia Committee, which as a full committee chairmanship would automatically have been subject to a caucus vote. But he wants to keep the chairmanship of the Africa subcommittee of the House International Relations Committee.

Yesterday's caucus action means there will be a caucus vote on that, if he is renominted for the subcommittee post by the full committee.

However, the caucus rejected by voice vote a Kostmayer move to require a convicted member to automatically give up the committee or subcommittee chairmanship until he has served his sentence or won an appeal.

Rep.Daniel Flood (D.Pa.) has been indicted on bribery and other charges. Flood is chairman of the labor-health, education and welfare subcommittee on appropriations and must stand for reelection, as do all appropriations subcommittee chairmen.

Yesterday's caucus action did not directly affect him. However, a move by Rep. Andrew Maguire (D-N.J.) to force indicted committee or subcommettee chairmen to stand aside until their case is disposed of by a court failed in a 180-to-36 vote.

Action on a move by Rep. Elizabeth Holtzman (D-N.Y.) to require a caucus vote on subcommittee chairmen indicted for a crime related to the holding of public office was deferred until January.

A Kostmayer move to require an automatic expulsion vote on a convicted member was also deferred.

Californians Roybal and Wilson were reprimanded by the House for their parts in the recent Korean case.

Wilson accepted $1,000 in cash from Korean businessman Tongsun Park but failed to report it when questioned in writing by the House ethics committee.

Roybal also accepted a $1,000 Park contribution and repeatedly denied it to the ethics committee.

Wilson heads a post office subcommittee and Roybal a subcommittee on aging.

Whether they continue as subcommittee chairmen is now up to their committees rather than the full caucus. But sources said the caucus action makes it unlikely they will be deposed.

Several members and Werthelmer charged there was a "double standard" working for Roybal and Wilson. They noted that three years ago, the Democratic caucus stripped former Rep. Rober L.F. Sikes (D-Fla.) of his Appropriations subcommittee chairmanship after he was reprimanded by the House for a conflict of interest.

It was noted that Sikes was a southern conservative while Roybal and Wilson were more liberal and had the large California delegation behind them. It's just that people have known Charlie Wilson and Roybal for years." said Rep. Matthew McHugh (D-N.Y.).

McHugh offered the key proposal that would have required a vote of the full caucus on any subcommittee chairman who had been convicted of a felony, censured, reprimanded or otherwise admonished by the House.

Rep. James Corman (D-Calif.) offered an amendment to delete the reprimanded members, Roybal and Wilson, from McHugh 's proposal. It carried by a 161-to-73 vote.

Wilson argued in his own behalf that the proposal amounted to ex post facto punishment. He said he accepted the reprimand,but had he known it might put his subcommittee chairmenship in jeopardy he would have fought it.

Corman argued there was difference between a reprimand and a censure and others argued Roybal's and Wilson's transgressions were not related to their chairing of subcommittes.

"I think if the House fomally reprimands a member, it's serious enough to decide his subcommittee chairmanship in the full caucus," McHugh said later. "Subcommittee chairmanships are not a right, they are a privilege."

"This is a vote on the integrity of the House. "This is not a club," said Rep. Toby Moffett (D-Conn.).

After adopting Corman's amendment to delete reprimanded members, the causus passed McHugh's proposal 235 to 7.