CAPE TOWN - Members of Parliament are preparing to vote for or against President Jacob Zuma.

On Monday, National Assembly Speaker Baleka Mbete announced she had heeded the call for a secret ballot.

Opposition parties have called her decision historic.

Leaders of the opposition says all MPs -- regardless of their political affiliation -- are protected in Tuesday's vote.

DA leader Mmusi Maimane said Zuma is unfit to hold the highest office in South Africa.

"We want to urge all members to say: Let us place the interests of the 58 million South Africans first."

Meanwhile, the ANC caucus in Parliament will meet on Tuesday morning to deliberate before the motion of no confidence debate.

Jacob Zuma is expected to attend the meeting.

Party Chief Whip Jackson Mthembu insists the motion will be defeated.