Staff working at a Wilko distribution centre in Nottinghamshire have pledged to go on strike following 'brutal' rota changes which will involve more frequent weekend work.
For a number of years, Wilko said staff at its distribution centres had worked weekends in response to customer demand.
It confirmed it was in talks with team members about standardising seven-day working at its distribution centres.
Union bosses, meanwhile, said members had pledged to take action amid fears about work/life balance.
More than 2,000 people work at distribution centres in Wales and Worksop which supply Wilko stores across the UK.
More than 90% of GMB members at the two sites said they would take action during a consultative ballot.
Gary Carter, GMB national officer, said: “More than 90% of our members are so angry they are willing to walk out – that shows the strength of feeling amongst staff. The new rotas are brutal.
"Wilko bosses have given no consideration to work/life balance – many people need consecutive rest days and time with their families.
“To cut this off will have implications for their health and wellbeing, their safety and their family lives. People feel they’re being forced out of the job after many years of loyal service.
“We’ve offered several alternatives to these enforced rota changes – but management don’t seem to be listening.
“Members now feel they have no option but to take part in a strike ballot.”
According to the union, talks were held after Easter to avert the dispute but it said talks had broken down.
The GMB said it would conduct a "full strike action ballot".
A Wilko spokesman said: "Our customers are hard-working families that shop seven-days a week.
"For several years now, team members in our distribution centres have worked weekends in response to customer need. This is already part of their existing contract of employment and our current discussions are about making this a more regular working pattern.
“We are incredibly disappointed to hear the GMB talk about taking a more disruptive course of action.
"We understand this topic is as important to our team members as it is to our customers.
"We are continuing to talk to our team members and their representatives about creating rotas which meet the needs of our customers while enabling a work/life balance.”
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