Cape Town - Speaker Baleka Mbete on Friday filed heads of argument to the Constitutional Court in the case on voting on a motion of no confidence by secret ballot in which she insists that the rules of Parliament do not make provision for it.
Mbete said she was personally not opposed to the notion of a secret ballot but the legislature had considered the issue in the past and elected not to provide for it.
"The collective majority of the National Assembly rejected the proposal."
The Constitutional Court was asked by the United Democratic Movement to rule that the Constitution obliged, or alternatively permitted, MPs to cast a secret ballot when voting on a motion of no confidence.
The UDM filed the application after the Democratic Alliance tabled its fifth motion of no confidence in President Jacob Zuma after he reshuffled the Cabinet at the of last month and removed Pravin Gordhan as finance minister.
A debate on the motion was scheduled for April 18, but postponed pending the outcome of the court application.
Mbete argued in her submission that should the court hold that the rules of Parliament were unconstitutional in this regard, the matter should be referred back to her office with an order to amend the rules.
The Inkatha Freedom Party and the Economic Freedom Fighters have thrown their weight behind the UDM's application.
The parties want ANC MPs to be allowed to vote according to conscience. EFF leader Julius Malema has said the opposition would need some 70 ANC MPs to break ranks and back the motion for it to succeed and result in Zuma's removal from office.
ANC chief whip Jackson Mthembu has made it clear that the ruling party's MPs will be expected to toe the line and vote down the motion.
Former president Kgalema Motlanthe has publicly differed, saying as elected public representatives MPs' first duty was not ANC loyalty and those who defied the whip should not be sanctioned.