Johannesburg - Workers of mining group Xstrata demonstrated in Johannesburg on Tuesday and handed a memorandum of demands to their employers, the National Union of Metalworkers of SA (Numsa) said.
"The company maintains unfair wage differentials among workers between production facilities," the memorandum charged.
"Xstrata Alloys has angered workers and instead of focusing on negotiations... they have decided to apply cheap apartheid-era tactics of bashing members."
The document claimed police were being used to deny workers their right to protected strikes.
"Numsa is very angry that workers who went into a legal and protected strike have been treated like common criminals," it said.
Workers were not benefiting from Xtrata operations and the union demanded the company implement "harmonisation of employment conditions, benefits and pay".
Xstrata was not immediately available for comment.