THE battle between the National Union of Mineworkers (NUM) and rival newcomer, the Association of Mineworkers and Construction Union (Amcu), has flared up again at Impala Platinum - pointing to the once-dominant NUM losing its grip on the platinum industry.

An illegal work stoppage at Implats' Rustenburg mines started on Monday evening. Workers refused to go underground "when they heard that some of their colleagues, essentially local Amcu leaders, had been arrested", an Implats statement said on Tuesday.

Clashes last week between supporters of the unions had resulted in one person admitted to hospital with a gunshot wound, and the arrests were related to this, Implats said. The strike continued yesterday, with most workers not coming to work, it said.

The world's second-largest platinum miner is losing 3000oz of platinum a day, worth about R36m. There was no indication when the strike would end, but the company did not expect it to be as protracted as the six-week, unprotected strike earlier this year.

"Then there was an element of better pay and there were emotive issues at play. What's happening now is quite clearly inter-union rivalry," Johan Theron, Implats group executive for people, said on Tuesday.

A well-placed source, who declined to be named because the situation at the mine was so tense, said NUM had lost control. "What does it tell them when most of the workforce is out and they didn't call them out?"

A labour specialist, who also declined to be named, said: "The fact that Amcu has brought out the total workforce, and without any visible resistance, indicates it has taken full control of that workforce and that NUM is no real force at this mine any more."

Amcu claims to have secured more than 10000 members at the Rustenburg operation, about half of the unionised workforce. The claim, which Implats is verifying, could put NUM's position as the dominant under threat and lead to a change in its legal status.

Amcu general secretary Jeff Mphahlele said his union was not behind the strike, but it had broken the NUM's majority representation.

"People are tired of NUM. They fail to deliver on their promises. We are just taking NUM members," Mr Mphahlele said on Tuesday.

NUM general secretary Frans Baleni conceded Amcu had made headway on the platinum mines.

"It's a temporary setback," he said, confirming that the NUM had not called the strike. "It's of great concern. We don't mind normal competition. We are really concerned about people being intimidated into doing wrong things. Our members are under attack. Violence is a weapon Amcu uses to make people toe the line."

Asked about the loss of control at Rustenburg, he said Amcu was recruiting members on the "basis of lies", something NUM was struggling to counteract.

"Their strategy is not sustainable because, over time, people see through them," he said. "They make temporary disruptions but they cause a lot of hardships for workers. The situation in Rustenburg is unique because people there are so easily influenced."

Mr Mphahlele denied his members were involved in violence. "We don't carry guns. We are not that kind of union," he said.

Amcu has been trying to gain recognition from platinum companies, finding a chink in NUM's armour because of what labour specialists described as the latter union's "lax" approach in looking after its members' interests in the platinum sector, compared with gold and coal - a point Mr Baleni of NUM refuted.

Lonmin, the world's third-biggest platinum miner, has also reported violence and intimidation related to union struggles.

"Successfully managing labour relations represents the biggest challenge to the industry at this time," said Ian Farmer, CEO of Lonmin, adding that labour dynamics on platinum mines was undergoing a "sea change".

"The rivalry for membership between the unions could be a feature for the foreseeable future, with the corresponding increase of risk of escalating costs and disruption to production," he said.