The New Zealand Council of Trade Unions says international support is picking up for the Marton meatworkers who have been locked out of their workplace for five weeks.
ANZCO Foods, which owns the Canterbury Meat Packers lamb processing plant, locked out 100 union members after they refused to take pay cuts and work longer hours during the peak season.
Two hundred others are working at the plant after signing individual contracts.
President Helen Kelly says the CTU has used its international connections to attract support for the Meat Workers Union.
She says the International Union of Food has begun an email campaign denouncing ANZCO's actions among its 6 million members and the unions of two Japanese shareholders of ANZCO have also expressed concern at the lockout.
Ms Kelly says one locked out meat worker, Amanda Chase, flew to London earlier this week to ask for the support of the UK's Unite union, the largest in the UK and Northern Ireland.
She says, as a result of that visit, Unite has written to supermarket chain Waitrose - which gets supplies of premium New Zealand lamb from ANZCO - suggesting the supermarket's reputation will be tarnished by the association with ANZCO if the lockout continues and is not resolved fairly.
The meat workers and the company are due to head back to the mediation table on Wednesday morning in a further attempt to reach agreement after earlier negotiations broke down.