Dozens of AFFCO meat workers have gathered in Wairoa in northern Hawke's Bay to protest against what they call an unfair contract offer by the plant's owner, Talley's.
The meat plant in Wairoa is one of the last two AFFCO plants where union members are refusing to sign individual contracts.
It is part of a long-running dispute to renegotiate a collective agreement which expired in December 2013. The Employment Court is due to hear the dispute in early October.
Union branch organiser Eric Mischefski said the workers were unlikely to give up their collective agreement before the employment court heard the dispute, as the new contracts represented significant changes.
"One of the things that has come out of the agreement is that you're required to be available any day of the week, night or day, seven days a week," he said.
"There's also a provision in there for the shortening of smoko breaks and, in this industry, there's a fair bit of gear to clean up before you can actually go to the smoko room."
Protester Justin Kaimoana, who has worked for AFFCO for about 20 years, described the workers as "one big family".
"[Talley's] is coming between families, which I don't think they realise they're doing," he said.
"Whether they do or not, I don't think they have a conscience. They're one of the richest families in New Zealand and now they're pitting family member against family member."
The non-union members at the plant had already signed the individual contracts, Mr Kaimoana said, because they had "got dollar signs in their eyes".
He said the workers protesting the new contracts would not back down.
"I guess we'll just go on for as long as it takes. Wairoa is not going to take a step back in terms of this," he said.
"We know we're in for a big battle with this company. They've got more money, more resources than our union has, but hopefully with the iwi and CTU [Council of Trade Unions] on our side, we'll be able to counteract the position they're in."
AFFCO said it was surprised the workers were refusing to sign the individual contracts.
It said the contracts were not that different from ones offered by other meat companies.
"The shift arrangements are standard industry arrangements, and our industry is a seasonal industry, however our employees at Wairoa in this last season have had one of the longest seasons with the best earnings for many years."