"This is in light of the president’s absence and that of the two other vice presidents who are both in South Africa," Tamborinyoka said.
Ailing Zimbabwean opposition leader Morgan Tsvangirai on Wednesday appointed one of his three deputies to take charge of the party while he undergoes cancer treatment in neighbouring South Africa.
Movement for Democratic Change (MDC) leader Tsvangirai's spokesman Luke Tamborinyoka said in a statement the former union chief had appointed Nelson Chamisa, 40, as acting president "until the president's return."
"This is in light of the president's absence and that of the two other vice presidents who are both in South Africa," Tamborinyoka said.
Tsvangirai who announced in 2016 that he had colon cancer, is undergoing treatment in South Africa.
Local media reported this week that his condition had deteriorated in recent days but the 65-year-old Tsvangirai refuted the claims in a post on twitter saying he was shocked to read that he was critically ill.
"Of course I have cancer and not feeling too well but I am stable and the process is under control," Tsvangirai said in a post on twitter, adding that "I am recovering."
Internecine feuding over Tsvangirai's success is threatening to tear the party apart ahead of crucial general elections in which new president Emmerson Mnangagwa has vowed a clean sweep.
Tsvangirai has led the MDC since its formation in 1999 and the party has posed the most formidable challenge to the ruling ZANU-PF party.