A Canterbury meat plant which is part of the Talley's group has been fined $28,000 after it kicked out and tried to trespass a union rep trying to recruit new members.
The Meat Workers Union says it is the largest Employment Relations Authority penalty for its kind of case.
The union took the case against South Pacific Meats after organiser Wayne Ruscoe made an agreed-to visit to the Malvern plant in May this year.
The ERA decision says Mr Ruscoe was handing out sealed envelopes to workers but refused to show what was in them to health and safety officer James McFarlane.
It led to a quarrel, caught on CCTV, over whether Mr Ruscoe could film and where he could go in the factory before a "burly" worker grabbed Mr Ruscoe and pushed him against a corridor wall.