Former president Jacob Zuma has failed to convince the Constitutional Court that Mandisa Maya, the former head of the Supreme Court of Appeal, grossly misdirected herself by refusing to reconsider his bid to force the removal of prosecutor Billy Downer from his corruption trial.

The apex court unanimously dismissed Zuma's argument that Maya - who President Cyril Ramaphosa has since appointed as the deputy chief justice - grossly misdirected herself when she found there were no exceptional circumstances justifying the reconsideration of her court's dismissal of Zuma's challenge to a ruling that Downer had the title (legal standing) to prosecute him.

Zuma had also asked that the Constitutional Court to grant him leave to appeal Judge Piet Koen's dismissal, in the KwaZulu-Natal High Court in Pietermaritzburg, of his special plea to the Supreme Court of Appeal.

While stating that it had not decided whether Maya's decision was, in fact, appealable, the country's highest court said it had "concluded that it would not be in the interests of justice to grant leave to appeal" Maya's decision, given that Zuma would be entitled to seek leave to appeal Koen's decision "to this court".

Zuma's foundation tweeted on Thursday that the ruling confirmed the former president "can exercise his right to appeal the adverse decision of the High Court to the Constitutional Court", but did not confirm that he would, in fact, do so.

Zuma is due back in court on 17 October.

He is pursuing a private prosecution against Downer and News24 journalist Karyn Maughan, who are both are challenging it as an abuse of court process.