The National Union of Mine Workers (NUM) has blamed striking miners, who are not members, for intimidation and threats against their colleagues at several mines.
The union insists it still enjoys support from a majority of workers in the country.
NUM has been widely criticised for its lack of leadership in protest torn mines especially in the North West in the past month.
Striking workers also claim NUM did not take up their grievances with mine managers.
Some of them have opted to join the newly formed Association of Mine Workers and Construction Union (Amcu).
NUM's Lesiba Seshoka says, "In certain areas, we are seeing an increase in levels of intimidation. Therefore you cannot blame the Num for unruly protesters."
Several mines have been hit by strikes in recent weeks.
Miners are demanding better salaries and improved working conditions.