Workers at one of Asda’s stores are to stage a 48-hour strike over claims of a “toxic” working environment.
Members of the GMB at the site in Gosport, Hampshire, will walk out on Friday until midnight on Saturday.
The union said its members had rejected a company offer aimed at resolving the row.
Regional officer Nicola Nixon said: “Counter-proposals have ben made to the company to settle the dispute but Asda has failed to come back with any improvements.
“Our members should be able to come to work without the threat of bullying or putting their health, safety and wellbeing at risk.”
An Asda spokesperson said: “We have met the GMB on several occasions recently, including mediation at Acas, to try and agree a fair solution for all colleagues in Gosport.
“The proposals we put forward include the appointment of an independent third-party organisation to establish the facts regarding GMB’s complaints and report back jointly to both parties.
“Unfortunately, this proposal was rejected by the GMB membership. As most Gosport colleagues are not members of the GMB and will continue to work as normal during this period, we are confident there will be minimal disruption to our operations”