A union leader says Solid Energy has increased the tension on the West Coast by running advertisements over a coal miners strike.
The state-owned coal miner took out full page ads in the Greymouth Star and the Westport News on Tuesday.
Hundreds of workers at the Stockton and Spring Creek mines are on a third week of strike action, supporting Waikato colleagues.
Ged O'Connell of the Engineering, Printing and Manufacturing Union says the advertisements accuse the union of leading workers by the nose, which he says is untrue and inflammatory.
Mr O'Connell says there is no sign of a breakthrough in the dispute.