Warehouse workers at retail giant Argos are to stage a three-week strike in a dispute over redundancy arrangements.
Members of the Unite union at sites across the UK will walk out on August 15 after a row flared over the transfer of hundreds of workers from a distribution hub in Leicestershire to a site in Northamptonshire.
Unite said it wanted guarantees that terms and conditions will be safeguarded, adding it was worried about the intentions of Argos, which is now owned by Sainsbury's.
National officer Matt Draper said: "We are faced with the thin end of the wedge with Sainsbury's pulling the strings behind the scenes, and the not-so-hidden agenda is serious cost-cutting to the detriment of our members.
"We want a comprehensive national agreement with the employer covering redundancy and severance packages."
Unite warned that the strike at sites in Essex, Somerset, West Yorkshire, Greater Manchester and Burton-on-Trent will affect deliveries, but this was denied by the company.
An Argos spokesman said: "We're disappointed with the union's actions, which are based on unreasonable demands and are wholly unnecessary. Customers can be reassured that we have full contingency plans in place to ensure there will be no disruption to deliveries."