The Meat Workers & Related Trades Union says seasonal lay-offs are becoming longer and more frequent at processing plants.
Following temporary lay-offs at Progressive Meats in Hawke's Bay, the union says seasonal lay-offs now for workers last up to four months rather than the usual one or two.
National secretary Dave Eastlake says it's unlikely that other work can be found during that time
Drought has contributed to a lamb shortage in the province for the past two seasons.
Mr Eastlake says weather conditions and a trend for farmers to convert their land to dairy production has meant a huge reduction in stock numbers across the country.
He says the union has 23,000 members in work at busy times of the year, but this number can drop to 7000 in off-peak months.