The British trade union GMB joined criticism of Amazon on Monday in the wake of allegations that the ecommerce firm mistreats staff at its head office in Seattle.
Elly Baker, lead officer for Amazon at GMB, told the Times that the company’s work patterns in the UK were causing physical and mental illness in its warehouses, with Amazon accused of a "chew them up and spit them out" attitude.
Among the problems she ascribed to this were stress, anxiety and musculoskeletal problems, which she attributed "specifically because of the regime they work under."
Some 7,000 staff are said to work for Amazon in the UK, with distribution centres located in Milton Keynes, Swansea, and Doncaster, among other places.
In June the firm rolled out a same-day delivery service in certain areas of London, with plans to extend it further in the British capital.
Baker’s comments come after a controversial piece in the New York Times described gruelling hours and an unforgiving attitude to health and personal crises at the ecommerce firm, which is now the biggest retailer in the world.
Among the anecdotal evidence of poor staff treatment was the tale of a miscarrying mother who was told she had to go on a business trip the day after surgery.
The ecommerce giant faced criticism for a warehouse in Pennsylvania in 2011 after it was revealed ambulances had been put on standby to rescue workers collapsing in the heat.
Amazon subsequently installed air-conditioning in the facility
Previously an Amazon executive had said the company "used to burn a lot of people to the ground", but he added such practices had since been reformed.
Responding to the New York Times piece Amazon chief executive Jeff Bezos sent an internal memo to staff slating the piece, saying he did not recognise the company it described.
"I don’t think any company adopting the approach portrayed could survive, much less thrive, in today’s highly competitive tech hiring market," he said.
"The people we hire here are the best of the best. You are recruited every day by other world-class companies, and you can work anywhere you want."