Jonathan Moyo said it was "unprofessional" for the army led by Constantino Chiwenga to intervene in November just because they didn't like the former first lady.
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"The fact that some people, who may in fact be a minority, may have issues with Doctor Grace Mugabe does not mean it is a crime to support her," Moyo said in a BBC HARDtalk interview on Thursday.
"You do not prevent an election through a military coup simply arguing that you do not like Grace Mugabe. It's unprofessional for an army to do that," he added.
Watch the video below as Moyo speaks during the interview
Moyo was a key member of the G40 faction that, until November 15, had the upper hand within the ruling Zanu-PF party. Grace Mugabe looked certain to become one of the country's two vice presidents following the sacking on November 6 of Emmerson Mnangagwa, who led a rival faction.
'A banana republic'
But the military takeover saw the expulsion from Zanu-PF of Grace Mugabe, Moyo and others linked to her. Mnangagwa replaced Mugabe as president.
Moyo said the army intervention had reduced Zimbabwe to a "banana republic".
"Zimbabwe's army under Chiwenga has joined the ranks of banana republics where military individuals intervene because they don't like this individual, or they like that individual," he said.
Chiwenga retired as defence forces commander last month, but was swiftly promoted to vice president. He is also the minister of defence.