The MDC-Renewal Team on Wednesday filed papers with the Constitution Court challenging the recent expulsion of its 21 lawmakers from Parliament.
The party, in the same breath, has vowed to boycott all pending by-elections triggered by the ejections until comprehensive electoral reforms are put in place.
The Renewal lawmakers were kicked out of Parliament after they were recalled by the Morgan Tsvangirai MDC following another party split.
MDC-Renewal spokesman Jacob Mafume told VOA an urgent application will also be lodged with the upper courts Thursday to force the return of the lawmakers into the backbenches.
"Without fundamental reforms we are not going to participate in the by-elections," Mafume said.
"We firmly believe that we have to protect our rights. Section 129 (k) as it is being used by the Speaker sends a chilling effect to internal party democracy."
The first major MDC split was in 2005 when Professor Welshman Ncube left Tsvangirai to form their own party.
But the MDC Renewal argues that they did not leave the party, just that they are trying to ignite debate on the need to reform the party, its structures and leadership.
Despite forcing the recall of the 21 lawmakers, the Tsvangirai MDC also says that it will not participate in the by-elections, leaving Zanu PF with a clear shot at collecting 14 of the seats that are up for grabs.