The party sent out a statement saying it would hold a media conference in Parliament on Thursday to “welcome Vytjie Mentor together with other people of influence who have chosen to join the ACDP over that of many other political parties”.
Party leaders would also give an update on its election campaign.
It is not yet clear what role Mentor will fill or how many others are expected to join on that day.
On her Facebook page on Tuesday morning, Mentor greeted her followers with “good morning world” and posted a photo of a slice of cake and the Bible opened up on a chapter of Samuel, which describes how unspiritual Saul became very spiritual and was later proclaimed king.
Mentor, who used to be a senior ANC MP and chairperson of the portfolio committee on public works, came into the spotlight in March 2016 when she claimed that the Gupta family offered her a post as a minister.
Besides talking about state capture and the Marikana shooting in her book No Holy Cows , she also detailed her alleged experience of the extent of sexual harassment in the ruling party.
Mentor gave her evidence to the Zondo commission of inquiry into state capture and was later cross-examined.
She took issue with several records that were put forward against her testimony, including SAA and Department of Home Affairs records.