from the National Prosecuting Authority.
This lawsuit is likely to exacerbate divisions between the pro-Ramaphosa and pro-Zuma camps in the ANC, who are both jostling for influence within the party and in government.
Mr Zuma has made no secret of his contempt for the president, a grudge that has been simmering since he was forced to step down.
In recent months, Mr Zuma been increasingly critical of the president's leadership. Making disparaging remarks is one thing but the attempt at a private prosecution has certainly turned up the heat, not least because of the timing.
If the ANC decides to take this matter into consideration at its conference then its step-aside principle could come into play. That says that anyone who has been charged with corruption or other serious crimes is barred from taking part in party activities until the matter has been cleared up.
But private prosecutions, which are unfamiliar territory for many in South Africa, are not a simple matter.
Very few are successful and they are often a lengthy and expensive process.
Mr Ramaphosa's other challenge is the fall-out from the report on his handling of the burglary at his farm.
Although he survived the vote in parliament, the report is expected to be discussed at the ANC gathering. Its leaders will decide whether to reject its recommendations or act on them.
One thing is clear - it will not be business as usual for Mr Ramaphosa at this year's meeting.
He has stepped into the conference a bruised man.
Additional reporting by Nomsa Maseko in Johannesburg