Drivers who deliver goods for Argos are set to go on strike just days before Christmas in a dispute over pay.
The union said the three day walk-out from next Tuesday threatened "mayhem" for Christmas deliveries though Argos said it had contingency plans in place and was working to prevent deliveries from being disrupted.
Members of Unite employed by Wincanton - a separate company - at a national distribution centre in Staffordshire are engaged in a dispute over holiday back pay.
Unite regional officer Rick Coyle said: "This strike by our members will cause havoc and mayhem to deliveries to Argos shoppers in the run-up to Christmas.
"There will be a lot of very unhappy Argos customers, if they don't receive the iPhones, TVs and white goods that they have ordered as presents for relatives this Christmas."
He said strike dates were only being announced as a last resort and that "Unite's door is open 24/7 to try and settle this long-standing dispute".
Argos said: "We would encourage both sides to keep talking with the aim of coming to a swift resolution.
"We also have contingency plans in place and can reassure customers we're working hard to ensure this will not impact our deliveries this Christmas."
The strike adds to the industrial chaos in the run-up to 25 December with hundreds of thousands of passengers being hit by action on the Southern rail network and Post Office workers planning a walk-out next week.
Unite said the dispute centred on how holiday pay is calculated after legal cases established that overtime and extra shift payments should be taken into account.
It said managers at Wincanton had offered to backdate additional pay to April, while it maintains this should go back at least two years, and that each driver is owed an average £700.
Wincanton had yet to provide a statement in response.
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