A major British supermarket chain has got involved in the pay dispute at the CMP Rangitikei meat processing plant near Marton in Manawatu.
More than 100 workers have been locked out since negotiations broke down on October 19.
Council of Trade Unions president Helen Kelly says the supermarket chain Waitrose, which buys New Zealand lamb from the plant's owners, ANZCO, has written to the company to settle the dispute.
She says ANZCO is ignoring that, as they haven't asked the union to get into mediation.
Helen Kelly says the union in the UK is now saying it will picket the Waitrose stores and boycott New Zealand lamb in order to put more pressure on ANZCO.