The GMB union is calling on Co-operative members to help oust Amazon lockers from the mutual's grocery stores.

The union, which has pursued a long-running campaign over pay and conditions at the online retailer's British warehouses, said it had already raised the issue with the Co-op's chief executive Richard Pennycook and was now calling on members to throw out a "cuckoo in the ethical nest".

"GMB needs the support of Co-operative members to ensure that Amazon improves security of employment, treats workers fairly and pays them a wage they can live on in their distribution chain in the UK and elsewhere in the EU," the union said. It claims that the majority of Amazon staff earn £6.39 an hour, only just above the national minimum wage, with permanent staff starting on £7 [ see footnote]. Amazon was unavailable for comment.

Amazon is putting lockers in 160 Co-op stores where shoppers can choose to pick up goods ordered online, after teaming up with the mutual in 2012.

The Co-op declined to comment.

• This article was amended on 18 August 2014. Following publication Amazon has asked us to point out that its permanent staff earn a minimum of £7.10 an hour and that outside of the run up to Christmas about 80% of employees at its warehouses are permanent.