The former federal judge appointed by the courts to rid the Teamsters union of corruption plans to veto the recent appointment of a top union leader with suspected ties to organized crime and has ordered members of the Teamsters General Executive Board to tell under oath why they approved the appointment.

Frederick B. Lacey, the independent administrator appointed last year to oversee the operations of the Teamsters until new elections are held next year, notified the 17-member board that he intended to "exercise my veto" of the appointment of Jack B. Yager as both a vice president of the union and as director of the Teamsters's politically powerful Central States Conference.

In a July 31 letter sent to every member of the board, including Teamsters President William J. McCarthy, Lacey said that, beginning Aug. 13, he would start questioning each of them about what they knew of Yager's background when he was appointed to the two posts, particularly about Yager's dealings with "members of the Civella Mob" as well as other organized crime figures while Yager worked in Kansas City for the late Teamsters president Roy Williams. Williams was convicted and served time in prison for his ties with organized crime while heading the 1.6 million-member union.

Lacey did not elaborate on his precise concerns about Yager. Efforts to contact him at his Newark office were unsuccessful.

The Teamsters leadership signed a consent decree last year to settle a civil racketeering suit in which the Justice Department charged the union had become, in effect, a wholly owned subsidiary of organized crime.

As part of the agreement, in addition to placing the union under a form of trusteeship, the union agreed to hold its first direct secret ballot elections of national leaders in a two-stage process beginning this fall and extending through the end of 1991.

In his letter, Lacey said "because of information that has come to my attention, I am prepared at this time to exercise my veto of Mr. Yager's appointment. However, before doing so, and in fairness to Mr. McCarthy, the members of the General Executive Board and Mr. Yager, I wish to take their testimony under oath with respect to the Yager appointment as a vice president and as a central conference director."

In the meantime, Lacey said Yager "should not undertake any duties," as either vice president or conference director. "I make this suggestion because, quite frankly, given what information I have about his background, it would have been more prudent for you to have submitted his name to me for investigation before clearing him for the appointment," Lacey wrote.

A spokesman for the Teamsters had no immediate comment on the Lacey letter. Teamsters General Counsel James T. Grady, who has frequently questioned Lacey's authority over internal union matters, was unavailable for comment. Yager, too, was unavailable for comment. His office said he was traveling this week.

Yager, who was McCarthy's hand-picked candidate, was appointed a union vice president last April. A union source said yesterday that McCarthy had assured the board at the time that Yager had been cleared by the government.

Two weeks ago, McCarthy named Yager director of the Central States Conference, replacing Teamsters Vice President Daniel C. Ligurotis of Chicago, who has drawn McCarthy's anger since hinting that he would challenge McCarthy for the union presidency.

Yager is president of Local 41 in Kansas City and has served a number of years as the union's national freight director coordinating trucking negotiations. He gave up that post when he was elevated in the Central States Conference.

Lacey's intervention comes at a time when the union leadership is reported in turmoil as various top leaders jockey to find a slate to run on in the new election process. None of the top union leaders has participated in a secret-ballot direct election for national office.