Supermarket giant Asda has started a consultation with staff over potential job losses next year which could total up to 2,500.
The chain told HuffPost UK it had already begun discussions with workers over the phone.
Asda has issued notices for five separate areas of work where jobs could be lost; combined back office, George clothing desks, petrol, hosting and bakery.
The plans include changes to workers’ hours, it is understood.
Gary Carter, national officer at the GMB union, said: “These proposed redundancies are a hammer blow to Asda workers. The timing of this announcement, in the run up to Christmas, is doubly appalling.
“Asda is performing well and is highly profitable because of the hard work of our members, who are the backbone of the company.
“These cuts make no sense whatsoever – slashing our members jobs would hurt the service Asda customers receive. GMB will fight tooth and nail for every single job.”
The news comes amid a proposed merger between Asda and fellow supermarket giant Sainsbury’s, which advertising watchdogs have previously warned could lead to store closures.
It said a statement the chain said: “In a competitive retail market, where customers rightly expect great value and ease of service, we must always look at how we can work more quickly and efficiently for them – and inevitably, that means we need to consider changing the roles we need our colleagues to do or the hours needed in particular parts of our stores.
“We believe the proposed changes we are consulting on would allow us to do a better job for our customers.
“We also recognise that discussions about potential change aren’t easy.”