South Africa's opposition Umkhonto We Sizwe (MK) party, backed by scandal-tainted ex-president Jacob Zuma, is allowed to stand in the May 29 general election, an electoral court ruled on Tuesday.

The Johannesburg court rejected a complaint by the ruling African National Congress, which said MK's name and symbol were so similar to those of the now disbanded military wing of ANC that this could deceive or confuse voters.

"We find there is nothing unlawful about the registration of MK by the DCEO (electoral commission) on September 7, 2023," the court said.

The ANC, which has been in power for three decades, had not properly explained why it had waited until January to ask for MK to be disqualified, according to the court.

"The ANC's explanation is irrational because it doesn't come close to justifying its delay in bringing the application late," said judge Lebohang Modibale.

The May general election, after which the victor will appoint a president, is set to be tense.

The ANC is on the brink of dropping below 50 percent of the vote for the first time since it came to power at the end of apartheid.

That would force the party once led by Nelson Mandela to form a coalition to stay in office.

The name of the radical opposition MK is identical to that of the armed wing of the ANC, which Mandela led from exile during the apartheid era.

Former president Zuma, who was forced out of office in 2018 under a cloud of corruption allegations, is campaigning for MK in a bid to relaunch his political career and weaken his former party, the ANC.

The latest opinion polls give MK 13 percent of the vote nationally.

It could do particularly well in Zuma's home province of KwaZulu-Natal. South Africa's second most populous province has the country's largest number of ANC supporters.

MK sought to register as a political party in June 2023 but the electoral commission rejected the move due to "patterns of discrepancies" in its signatures.

MK modified and resubmitted its application and was formally registered in September, the court said during Tuesday's short hearing.

Four months later, the ANC contested the move, arguing that "MK's registered name and its distinguishing mark and symbol" were so similar to those of the ANC that this could "deceive or confuse voters".

But the court ruled on Tuesday that the ANC had reacted too late and the reasons it gave for doing so were unconvincing.