According to a report in the Sunday Telegraph, the 25% shareholding in Imago Young & Rubicam was sold last month for $1 (54p) to Sharon Mugabe, the majority shareholder and chief executive.
Sharon Mugabe was named as the architect of the ruling party Zanu-PF's campaign for re-election in June, although WPP says it was assured she had no relation to the president. She had bought the controlling stake in the agency from its white owner in 2006.
The election was marked by intimidation and violence toward voters. The opposition party, the Movement for Democratic Change, pulled out after deciding its supporters' lives were at risk.
WPP chief executive Sir Martin Sorrell reacted by ordering the 25% stake be sold, while Bernard Barnett, WPP's corporate vice-president EMEA, said: "This is a disgraceful regime and we want no connection between Y&R and it."
One condition of the completed sale is that Imago Young & Rubicam changes its name to remove all references to Young & Rubicam and associated brands.