Logistics workers at Morrisons are being balloted for strike action following claims that staff were being forced to increase their pension contributions while the supermarket reduces its own.

The Unite union warned supermarket shelves would be empty if the 1,000 workers in Cheshire and Wakefield voted to down tools and walk out over the spring and summer.

It said the pension changes being imposed would leave staff worse off by around £500 a year and it accused Morrisons of “flagrant profiteering”.

The staff work in a variety of roles, including warehouse stock controllers, lorry loaders, canteen staff, cooks and administrators.

Unite added that additional changes workers were being compelled to adopt included a new “pick rate”, which monitors the speed at which items are packed from warehouse shelves, the removal of a service award, enforced changes to jobs roles and a failure to correctly follow absence policies.

Unite national officer Adrian Jones said: “Our members provide a vital service ensuring supermarket shelves are full.

“Yet Morrisons have decided to unilaterally impose changes to their pensions that will leave them worse off and changes to the conditions that no one wants.

“Morrisons need to see sense and reverse these changes or they will see the anger of our members on the picket line.”

The ballot for Unite members opened on 18 April and closes on 9 May. The union warned that if the ballot was successful and if no concessions were made by the employer, industrial action would take place this spring and summer.

Morrisons told Motor Transport it would not be commenting on the matter.