The UDM on Tuesday added its endorsement to a motion of no confidence in National Assembly Speaker Baleka Mbete.

"Before she was elected into office, the Speaker is on record distorting and attacking outcomes of the Public Protector's investigations on Nkandla," United Democratic Movement leader Bantu Holomisa told MPs.

Speaking during a debate on the matter, characterised by loud heckling, frequent angry interruptions and spurious points of order, he said her objectivity was questionable.

"This distortion and attack has since been sustained by the organisation she presides over as its National Chairperson. In this regard, her objectivity on the work of the parliamentary committee considering this matter is highly questionable."

It could also compromise the independence of the House.

"Irrespective of the outcome of this process, today, surely we can all agree that there is a great and urgent need to evaluate whether Parliament has been discharging its mandate over the last 20 years in accordance with the principles of inclusive participatory democracy," he said.