(AFP) - South Africa's former President Jacob Zuma was suspended from the ruling African National Congress (ANC) on Monday, weeks after he backed another party ahead of this year's general elections.

The decision, which was widely expected, will be seen as a further sign of disunity in the movement ahead of this year's vote, in which the long-dominant ANC is expected to lose ground.

ANC secretary general Fikile Mbalula said Zuma would undergo a disciplinary process and the party would take legal action against the rival political group campaigning in his name.

"Zuma, and others whose conduct is in conflict with our values and principles, will find themselves outside the African National Congress," Mbalula told a press conference.

Zuma was the fourth president of democratic South Africa from 2009 to 2018 but was forced from office under the cloud of corruption allegations and he has become estranged from the party he once led.

In December, he declared that he would be campaigning for a new party, uMkhonto We Sizwe (MK) or Spear of the Nation, named after the ANC's former armed wing during the anti-apartheid struggle.

However, he did not quit the ANC, leading some analysts to speculate he was hoping to be expelled in a play to garner more support.

He has since been a thorn in the side for the ANC, which, in power for three decades, is bleeding support amid a weak economy and allegations of corruption and mismanagement.

Polls suggest Zuma's departure threatens to cost the party more votes.

Earlier this month, a survey found almost one in three South Africans approve of the embattled former president, with support for the 81-year-old particularly strong in his home province of KwaZulu-Natal -- a key electoral battleground.

- Barred from standing -

President Cyril Ramaphosa, in an interview with state broadcaster SABC following the announcement said "once you define yourself as being allied to another party you bring into question your own membership and that is why the NEC took the decision that it has taken".

The head of state confirmed that the party had tried to reach out to Zuma before the decision, adding that Zuma's move was "a total suprise".

Mbalula said that in addition to suspending Zuma, the ANC would complain to the electoral court to get MK deregistered and mount a trademark challenge to recapture the name.

"The formation of MK party is not an accident," Mbalula declared after a meeting to the ANC's National Executive Committee, attended by Ramaphosa.

"It is a deliberate attempt to use the proud history of the armed struggle against the apartheid regime to lend credibility to what is a blatantly counter-revolutionary agenda."

A charismatic figure, Zuma, has long been bitter about the way he was forced out of office in 2018 and replaced by Ramaphosa, then his deputy.

Relations between the two have since been tense, with Zuma last month denouncing Ramaphosa's government as "sellouts and apartheid collaborators".

Zuma, who is facing graft allegations, has already served two terms as president and has a 15-month conviction for contempt of court, so under the constitution he is barred from standing for elected office.

"The renewal of the ANC continues unabated, we continue to renew ourselves, we continue to improve ourselves and on that... forward movement we will find that there are those who fall off" Ramaphosa said.

© Agence France-Presse