The South African Communist Party has chosen to side with the ANC on the vote of no confidence against President Jacob Zuma.
The SACP is the ruling party's alliance partner and has around 17 members in Parliament on an ANC ticket.
The party has called for Zuma to resign, but say they will not side with opposition who have an "agenda to dislodge the ANC".
"The SACP is in alliance with the ANC, we cannot join an opposition agenda to dislodge the ANC," said Alex Mashilo, spokesperson for the party.
"We have not isolated SACP members who are ANC MPs before. We will also not do so this time around because they are governed by the principals governing the relationship between the SACP and the ANC."
Mashilo said the SACP's constitution states that its members who are active in fraternal organisations, like the ANC, are bound be the decisions made by those organisations.
"The constitution of the SACP directs how they should conduct themselves when they represent other organisations. In Parliament, they are not exclusively representing the ANC. The ANC did not contest elections only on behalf of its own members, it contested elections also on behalf of its alliance partners," Mashilo said.
"There is a constitutional court ruling on this matter. But we have not told anyone how to vote."
But the SACP has also asked for Zuma to step down voluntarily.
"We remain faithful to that process [that the president must resign]. While that process was unfolding, the opposition parties launched the motion of no confidence in parliament and they have since said that the motion is not aimed at the president alone; it is aimed at the entire ANC," Mashilo said.