Two labor organizations filed a complaint with the Labor Department yesterday asserting that the Teamsters union selects its presidents illegally and asking the department to draft new rules that would involve the 1.8 million members more directly in elections.

"This is the Achilles' heel of the Teamsters union. This is the method they have used to have a string of bad apples elected in the union," said Arthur L. Fox II, a lawyer for the Public Citizen Litigation Group, which represents Teamsters for a Democratic Union (TDU) and the Association for Union Democracy.

Teamsters presidents are chosen by delegate votes every five years at a national convention, according to the union constitution. Most voting delegates are local Teamsters officers and business agents who automatically become delegates under the constitution.

The groups' petition asks the department, which oversees union elections, to enact a rule requiring unions to elect convention delegates from local union ranks no more than 120 days before national officers are chosen. Current rules require election of convention delegates but do not say how or when.

Most unions use direct elections or elections of convention delegates who choose national presidents, with the Teamsters the only major union to use its process, according to TDU, a Detroit-based Teamster dissident group. Fox said Teamsters presidents are chosen by local officers elected as long as three years before each convention, a process that "robs the membership" of any meaningful influence. "Were the Teamster model to be followed in the case of the next U.S. presidential election, we would go to the polls in 1985 . . . to vote for the Electoral College" that would pick a president three years later, the petition said. Teamsters officials were unavailable for comment.

Teamsters President Jackie Presser was named in 1983 by the union executive board after the indictment and resignation of President Roy Lee Williams. He is to stand for election in May.