Marks & Spencer has been accused of putting 183 workers' jobs in jeopardy by switching suppliers of deli fish products.

The Unite trade union said this week that the management at the Coldwater Seafood plant in Redditch had begun a 90-day consultation procedure on proposed redundancies after M&S announced it was to seek an alternative supplier.

"This decision is disastrous for workers at Coldwater," said Unite regional industrial organiser Joe Clarke.

"M&S sources its delicatessen seafood products from this Coldwater plant, and about 80% of the range at the site is produced purely for M&S. To some extent Coldwater has been locked into an arrangement with M&S that has meant it has been restricted from supplying other retail companies with the deli range of its seafood products."

M&S had a responsibility to the 183 workers who had worked hard to supply the retailer with high-quality fish, Clarke added.

Unite would campaign vigorously to reverse this decision, he said, branding it "wrong and unethical" for M&S to move away from a supplier that had dedicated itself to the supermarket for many years. A spokesman for M&S said it hadn't taken the decision lightly and there were plans to continue sourcing seafood products from the Grimsby plant of parent company Icelandic Group UK.

Meanwhile Unite has also organised a number of rolling protests over the next few weeks in a bid to highlight what it has called M&S's "unfair" treatment of workers throughout its supply chain.

The union is preparing to demonstrate across the UK, including Northern Ireland, as well as at M&S operations in Turkey and Hungary. "Justice for low-paid workers is the least we should expect from a brand that claims to have corporate social responsibility at the top of its agenda," said Unite joint secretary Tony Woodley. "It is time M&S delivered."