Image caption The Asos warehouse is located at the Houghton Main Colliery Roundabout and employs about 4,000 people

JD Sports and Asos have been accused of running their warehouses like "satanic mills" after figures showed the number of ambulance callouts to their sites.

Ambulances were dispatched 40 times to JD Sports' troubled Rochdale site last year, while there were 45 callouts to the Asos warehouse near Grimethorpe.

Union Unite said the figures reignited concerns about working conditions.

Both employers emphasised the importance they placed on the health and safety of all staff.

The figures, based on Freedom of Information requests, showed that ambulances were called out to the Rochdale warehouse 117 times over the past three years and 148 times to the Asos site in South Yorkshire.

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The sports chain, headed by Peter Cowgill, was forced to start an investigation in 2016 into conditions at Rochdale, after an undercover film showed staff allegedly paid less than the minimum wage and treated "like cattle".

Responding to the figures, Matt Draper, from Unite, said: "The warehouses of some companies risk becoming the dark satanic mills of the 21st Century."

Neil Derrick, GMB regional secretary, said Asos bosses "appear to be in denial about the inhumane conditions people have to work under" at the Barnsley.

He said: "They are making millions while workers are literally being taken away in ambulances."

Image copyright JP Sports Image caption JD Sports' Rochdale site is the company's main warehouse

The figures do not detail why the ambulances were called out, but previous instances of poor working practices in warehouses include staff subject to timed toilet breaks, invasive security checks and exhausting targets.

Among the other retailers included in the data, 21 ambulances were called to the Amazon warehouse in Warrington in 2018, six to its site in Doncaster and one to its Water Vole Way unit in the town.

The figures also show that Sports Direct's ambulance callout rate had improved since the scandal around working practices at its Shirebrook site.

Responding to the figures, a spokesman for JD Sports said given the scale of its operations, the number of incidents in which an ambulance was called out was "proportionally very low".

Asos and XPO Logistics, which runs the Barnsley site, said: "Since 2013, the accident/incident rate has declined considerably year-on-year and has remained significantly below the industry standard throughout this period."

Amazon responded claiming it had more than 40% fewer injuries on average than other transportation and warehousing companies in the UK.