South Africa’s ruling African National Congress has suspended an influential party official for refusing to step aside over corruption charges, a key victory in a long battle by President Cyril Ramaphosa to assert control over the party.

Secretary-general Ace Magashule was ordered to step back from his powerful role overseeing the day-to-day running of the ruling party, after defying a deadline to step aside voluntarily, according to an ANC letter seen by the Financial Times and local media. The ANC confirmed that letters had been sent to members who had refused to step aside.

The suspension removes a key opponent of Ramaphosa’s from a party that has been divided since he replaced the scandal-hit Jacob Zuma as president four years ago.

Supporters of Magashule, a Zuma acolyte, and allies of Ramaphosa have fought over the direction of the stagnant economy and a clean-up of corruption. “The suspension of Magashule is indeed a seminal moment for the ANC,” said Khaya Sithole, an independent analyst. “It really has been a house divided that Ramaphosa has been trying to manage,” he said.

Zuma is alleged to have allowed the Guptas, a business family, to control cabinet appointments and state contracts for the benefit of their mining-to-media empire. Ramaphosa last week admitted that the ANC allowed systematic looting over the past decade “under our watch”, the most direct acknowledgment yet of the party’s failings in the so-called state capture era.

As a party baron in South Africa’s central Free State, Magashule was part of a “premier league” of provincial leaders who backed Zuma through his many scandals. Even as Zuma fell from grace, Magashule remained secretary-general.

Magashule used the position as a pulpit to promote radical economic policies that embarrassed Ramaphosa, and he also defended Zuma amid his own mounting troubles with the law. But his power began to crumble last year when he was charged with corruption, fraud and money laundering in connection with the alleged looting of government contracts in the Free State, claims he denies.

Last month the party gave all members officially accused of corruption and other serious crimes 30 days to step aside from their posts or be suspended.

While suspended Magashule “may not make public pronouncements on matters related to the organisation” or mobilise ANC structures including over his stepping aside, the letter announcing his suspension said. His suspension will be in force until the “final outcome” of the corruption case but will be reviewed by senior party officials every six months, the letter said.

Magashule is likely to appeal against the decision by senior ANC officials, analysts said. “My suspicion is that he will appeal, but that he will lose” because the step-aside rule was clear and his court case is pending, Sithole said.

But “the bigger problem for Ramaphosa unfortunately” was that Magashule could yet find a way to mobilise against his leadership over the next year, Sithole said. “This is definitely not the end of Ace Magashule.”