Members of Parliament are the voice of the people of South Africa and must not act as the voice of their own political parties, former president Thabo Mbeki said.

In a letter published in the The Star newspaper, Mbeki, in reference to the motion of no confidence in President Jacob Zuma to be debated in Parliament on Tuesday, April 18, said MPs do not have to vote according to party lines.

"It is therefore obvious and logical that Members of Parliament (MPs), each elected to this position by the people as a whole, and never by individual political parties, including their own, must act in Parliament as the voice of the people, not the voice of the political parties to which they might belong," he said in the letter.

The ruling party has confirmed that they would be voting against the motion.

All opposition parties have vowed to vote in favour of the motion and appealed to the African National Congress (ANC) to do the same, as the party has the majority vote in Parliament.

"This poses the question all Parliamentary parties must answer – is this what the electorate expects of its elected representatives?" Mbeki asked.

Mbeki said the Constitutional Court, in the March 31, 2016 judgment on the Nkandla matter, defined the role of MPs.

"It stated, correctly, that our MPs serve in Parliament as representatives of the people. They do not serve in Parliament as representatives of political parties, even as they are members of these parties."

He said all MPs of all parties served as members because they were elected by the people of South Africa and were therefore accountable to this electorate – the people.

"There is absolutely no MP who sits in Parliament by virtue of being elected by the political party to which they might belong, including those who subsequently get elected by Parliament to serve as Head of State and government."

This boiled down to questions the MPs should ask themselves.

"Do I serve in Parliament to promote the interests of my political party; or, do I serve in Parliament to promote the interests of the people; and, is it possible that there might be particular circumstances, and particular issues, when I consider that the interests of the party and those of the people coincide, and what actions should I take in this context?

"It may be that the current political controversy has, at last, imposed on our country the opportunity and obligation the better to define the Constitutional and moral relationship between the people and their elected representatives."

The motion follows President Jacob Zuma's controversial Cabinet reshuffle, which saw Finance Minister Pravin Gordhan and his deputy Mcebisi Jonas being axed, among others.

This led to a downgrade to 'junk status' by ratings agencies Fitch, and Standard and Poor's, along with nationwide protests against Zuma.