National Assembly Speaker Baleka Mbete does not have the power to withdraw the motion of no confidence in President Jacob Zuma, Parliament said on Wednesday.

Only Democratic Alliance (DA) leader Mmusi Maimane could withdraw the motion, as he had asked for it.

Opposition parties have called for the motion, scheduled for next Tuesday, to be postponed. This was after the Constitutional Court on Tuesday granted the United Democratic Movement (UDM) direct access to argue its case that MPs be allowed to vote via secret ballot.

The court gave parties wishing to oppose the application until 12:00 on Thursday to file papers, and the UDM until 16:00 next Wednesday to file its reply.

Parliament on Wednesday said they had received correspondence from the UDM and Economic Freedom Fighters (EFF), asking Mbete to postpone the debate.

Mbete had already responded to the UDM and would respond to the EFF, spokesperson Moloto Mothapo said.

"The Motion of No Confidence, which the Speaker scheduled for 18 April 2017 at 14h00 in the National Assembly, in line with the urgent request, is tabled under the name of the Leader of the Opposition, Mr Mmusi Maimane. Therefore, in terms of the provision in the rules, only Mr Maimane - and not the Speaker - has the power to withdraw the motion," Parliament said.

The DA on Tuesday wrote to Mbete, asking for the motion to be postponed.