South Africa's ruling ANC suspended the country's former president Jacob Zuma from the party on Monday and vowed to launch a legal challenge against a rival group campaigning in his name.

Announcing the decision, ANC secretary general Fikile Mbalula declared: "Zuma, and others whose conduct is in conflict with our values and principles, will find themselves outside the African National Congress."

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

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.

Former South African President Jacob Zuma, sits in the High Court in Pietermaritzburg, South Africa, on October 26, 2021. Photo: AFP

Mbalula said that in addition to suspending Zuma, the ANC could complain to the electoral court to get the new party 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 party's National Executive Committee, attended by President Cyril 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."

Zuma has a 15-month conviction for contempt of court after refusing to testify before a panel probing financial corruption and cronyism under his presidency. 

His jailing sparked protests, riots and looting that left more than 350 dead in the worst violence to hit the country since the end of apartheid.

Under the constitution he is barred from standing for elected office.

However, a poll found last week that almost one in three South Africans approve of the former president, whose new political venture is expected to cost the ruling ANC votes in this year's elections.

Support for the embattled 81-year-old was particularly strong in his home province of KwaZulu-Natal -- a key electoral battleground -- with 63 percent of respondents there saying they felt warmly about him, according to the Social Research Foundation (SRF), a pollster.

The general election is expected to be the most competitive vote since the advent of democracy in 1994.

In power for three decades, the African National Congress (ANC) is bleeding support amid a weak economy and allegations of corruption and mismanagement.