The politicians, all of whom, are Members of Parliament are demanding that President Kabila respects the national constitution by allowing Katumbi to return to the country and participate in the December 23 elections without any form of threat.
The parliamentarians known as senators and deputies state that the government through the office of the Attorney General were abusing its powers and targeting Katumbi through politically motivated manouvers.
Katumbi recently had his passport revoked, a decision the senators and deputies have challenged.
The popular former Katanga governor is a leading contender to take over the reins from President Kabila who is constitutionally barred from seeking re-election.
Katumbi and six others, including an American national, are to go on trial before the Supreme Court of Justice. his lawyer Mumba Gana said.
The six face charges of “harming domestic security” all of which they deny as false and politically motivated.
Katumbi is accused of recruiting and arming mercenaries after falling out politically with Kabila in late 2015.
The 50 pro-Katumbi MPs and senators lashed the trial as “nothing but a shame for the highest authority of the state, which you embody.”
“Hatred for political adversaries, personal ambition or thirst for power cannot authorise judicial harassment against a citizen,” the letter, published by the DRC media, states.
It added: “It is difficult to believe in the sincerity of your declarations about the holding of democratic elections in our country on December 23… so long as you have not put an end to all the fake scandals concocted against Moise Katumbi.”
Katumbi leads a coalition of opposition political parties under the banner Ensemble as they seek to replace Kabila during elections in December.