Africa's oldest leader, Robert Mugabe, 93, has ruled the former British colony since independence in 1980 but has insisted that ZANU-PF, not himself, will choose his eventual successor.
But at a meeting of ZANU-PF's women's wing in the capital Harare, Grace Mugabe - herself considered by some to be a possible future leader - contradicted her husband, who also attended the meeting, saying he should name a successor.
Grace, 52, who has become a power broker in ZANU-PF since her elevation to the top echelons of the party in 2014, said Mugabe's word was "final".
"There is no succession which will take place without the involvement of Mugabe. I know the president says: 'No, no, I don't want to impose a candidate.' But I have always argued with him that you have a role, you have the right to be part of that process," Grace said at the meeting attended by reporters.
"Because we respect him, his word will be final. Mark my words, his word will be final. I am asking him right now in your presence ... don't be afraid, tell us which candidate we should back," Grace said, speaking in the Shona vernacular.
Mugabe did not respond to his wife's comments but earlier addressed the meeting, where he repeated accusations he made in December 2015 that some in the military leadership were caught up in the succession fight.
-The Star