Up to 230 jobs are under threat at a milk processing plant in Hatfield Peverel.
Owners Arla say it may close in the summer.
Work would be transferred to its new, £150 million, high-tech site in Buckinghamshire.
The trade union Unite wants urgent talks on the proposals.
Officials say they’re also concerned about a plan to transfer a further 32 logistical/driving staff to Bidvest Logistics.