Rep. Charles C. Diggs Jr. (D-Mich.), whose conviction on mail fraud and other charges is under appeal, decided yesterday not to make a congressional tour of 10 African and European capitals he had planned for this fall.

The trip, for which Diggs had received permission from a federal judge on Wednesday, had drawn objections from other members of Congress, according to both an aide to Diggs and House Foreign Affairs Committee chairman Clement Zablocki (D-Mich.)

Zablocki said last night that Diggs had "voluntairily canceled" the trip "after persuasion." Diggs' administrative assistant said Diggs had "postponed the trip" for "a number of reasons, some having to do with the situation in Africa, [and] some having to do with the situation in the Congress."

Diggs was censured by the House after his conviction Oct. 7, 1978, on charges of mail fraud and illegally diverting more than $60,000 of his congressional employes' payroll to his personal use.

None of the terms of the censure placed any restriction on Diggs' foreign travel, said the aide, Jack Barthwell. "Now we're told there's opposition . . ."

Diggs had asked Zablocki Oct. 9 for authorization to travel from Oct. 24 to Nov. 10 with stops at Madrid; Algiers; Niamey, Niger; Ouagadougou, Upper Volta; Bangui, Central African Republic; Douala, Cameroon; Santa Isabelle, Equatorisl Guinea; Lagos, Nigeria; Freetown, Sierra Leone, and London.

Zablocki said he had given a conditional authorization for the trip, contigent on at least one other member of the committe going.

Zablocki said he tried recently to persusade Diggs not to go, arguing that other committee members were not going, that Congress would be in session part of the time and that many other members felt Diggs' conviction should bar official foreign travel. Diggs' aide said the proposed itinerary included few glamor spots that would attract others to the trip.