The African National Congress faces a challenge to its dominant hold on power after the former leader of South Africa’s main commercial region threw his weight behind the formation of a breakaway party.

With Mbhazima Shilowa as their frontman, the secessionists who last week quit the party partly in protest at the ousting of Thabo Mbeki as president, stand a chance of depriving the ANC of the two-thirds parliamentary majority it has enjoyed since the end of white rule in 1994.