Updated

A renowned South African anti-apartheid activist will on Saturday launch a new opposition party to challenge the ruling ANC in elections next year.

Hundreds of supporters gathered in Pretoria for the formal launch of Agang SA by Mamphela Ramphele, 65, a respected academic who fought against white-minority rule.

Ranphele received endorsement on the eve of her party's launch from Nobel peace laureate Archbishop Desmond Tutu.

"Few thinking South Africans would not welcome the entry into South African politics of someone of the calibre, background, intellect and resourcefulness of... Ramphele," said Tutu.

Ramphele, a medical doctor, was a member of the anti-apartheid Black Consciousness Movement founded by her long-term partner Steve Biko, who was killed in police custody in 1977.

She will urge voters to back her party ahead of national elections next year. She has criticised the ruling African National Congress (ANC) party, for being corrupt and ineffective.

The ANC has been the ruling party since 1994, when apartheid rule ended with the election of Nelson Mandela as the country's first black president.

Brandishing its historical legacy in the fight against apartheid, the ANC has maintained a firm grip on power, but has come under increasing pressure over its perceived failures to deliver on its promises.