Around 180 jobs are at risk at Allied Bakeries in Cardiff after the Kingsmill bread-maker revealed plans to halt production at their facility in the city.
The group could stop bakery production at the site on Maes-y-Coed Road as part of a review after it lost a major own-label contract earlier this year.
Allied Bakeries said it will move baking to other facilities in the UK, but will continue to run its transport logistics depot from the Cardiff site, supplying bakery products across Wales and parts of England.
The Bakers' Food and Allied Workers' Union (BFAWU) said the announcement was ''devastating for Wales.''
''A lot of this is down to the power of supermarkets.'' BFAWU General Secretary Ronnie Draper said.
''They shift a product from one manufacturer to another without thinking about the consequences on jobs.''
Allied Bakeries is owned by Associated British Foods, which also owns high street fashion chain Primark and tea brand Twinings.