Amazon has been accused of "wasting millions" on a major advertising campaign calling for customers to visit its warehouses.
In recent weeks, the retail giant has invited customers to "take a look" at the company's operations in places like Milton Keynes and Peterborough following negative coverage over conditions.
But the GMB union called the move a stunt and demanded the company use its resources on staff to "stay safe and healthy at the end of their shift".
It comes after recent reports found that an ambulance was called out to a UK Amazon warehouse once every two days last year, with staff reportedly breaking bones, collapsing and suffering serious falls.
The new TV adverts include workers at the company praising Amazon as an employer before asking viewers to "take a look for themselves" by visiting their local fulfilment centre.
Amazon said that "tens of thousands of people" have now visited its 17 warehouses across the UK but it is keen for more people to witness its inner workings.