South Africa's biggest union is considering pulling out of the ANC-aligned Congress of South African Trade Unions (COSATU) labour federation to form its own political entity, a split that could hurt the ruling party in next year's elections, senior union sources said.
The National Union of Metalworkers of South Africa (NUMSA) is increasingly at odds with the African National Congress (ANC) and COSATU - part of an official, three-way governing alliance that also includes the Communist Party - over labour policies it says are too pro-business.
Coupled with anger at a perceived increase in corruption under President Jacob Zuma, the 350,000-strong union is now on the brink of walking out on a 25-year relationship forged in the common struggle against white-minority rule.
If NUMSA took some smaller unions with it, COSATU – the ANC's most effective 'get-out-the-vote' machine - could lose half a million members who would normally have campaigned faithfully for Nelson Mandela's former liberation movement.
NUMSA officials told Reuters union bosses were circulating a document ahead of a key December meeting asking whether it should form a labour party, civic movement or a worker federation to go head-to-head with COSATU.
"It is a draft document which will be discussed at our congress but it shows that we are not happy in COSATU and in the alliance with the ANC," one union official, who did not want to be named, told Reuters.
Although there has always been tension in the so-called 'Tripartite Alliance', since the end of apartheid in 1994 no union has threatened to withdraw its support for the ANC.
The crisis in the movement claimed its first high-profile casualty this week when NUMSA President Cedric Gina quit, saying he was unhappy with the anti-ANC stance being adopted.
"All is not well in NUMSA," he told Reuters. "I hope that the union will allow members to take their own decision on who to support in the elections."
A NUMSA political force would be likely to appeal to the disaffected youth also being courted by arch Zuma-baiter Julius Malema, an expelled ANC youth leader who launched the radical leftist Economic Freedom Fighters party this year.
Although there is no chance of the ANC losing its majority next year - it won nearly 66 percent of the vote in 2009 – both entities would erode its support on the left, and increase the chances of a sub-60 percent result, an outcome that would heap pressure on the scandal-plagued Zuma.
As with Malema, NUMSA General Secretary Irvin Jim, a firebrand advocate of large-scale nationalisation, helped Zuma become ANC leader in 2007 but is furious that the unions have since been relegated to an alliance "labour desk" and excluded from big decisions.
In a sign of its concern, the ANC has sent in its top enforcer, Secretary General Gwede Mantashe, to restore order although in reality it may be more like damage limitation to ensure the defectors are as few as possible, analysts say.
"The tension that has beset the ruling alliance since its inception has crossed some sort of boundary. The only thing keeping it together is institutional momentum and sentimentality," said BNP Paribas Cadiz Securities political analyst Nic Borain.
"It's only a matter of time before a split is formalised, but the ANC is not just going to roll over."