Amazon has become a ubiquitous feature of modern life. You can find almost anything on its website, and whatever it is you want – books, music, film – Amazon can get it to you the very next day or even sooner. We all know what Amazon does, but only now are we gaining a better understanding of how Amazon does it.

Lately Amazon has been on the receiving end of criticism over the way it treats its workers as well as how much it pays them. At the forefront of this campaign has been Senator Bernie Sanders. Sanders has introduced a bill designed to force companies such as Amazon to pay their workers higher wages. Amazon is one of the biggest employers of those who receive food stamps in the United States, with nearly one in three Amazon workers on food stamps in Arizona and one in 10 in Pennsylvania and Ohio.

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Sanders has also been highlighting some of the 19th-century working practices used by Amazon to control and discipline its workforce inside of its fulfilment centres. Sanders’ bill – the Stop Bad Employers by Zeroing Out Subsidies Act, or the ‘Stop Bezos Act’ – would tax employers like Amazon when their employees require federal benefits.

The Senator is right to push Amazon on this. But he is also right to highlight the company treatment of its workers. I worked undercover as an order picker at one of the company’s warehouses for three weeks in 2016, in the small Staffordshire town of Rugeley in the United Kingdom. I took the job as part of the research for my book, Hired: Six Months Undercover in Low Wage Britain.

The warehouse employed about 1,200 people. Most of my co-workers were immigrants from eastern Europe, predominantly Romania. During shifts of 10 and a half hours, it was our job to march up and down the long narrow aisles picking customer orders from two-metre-high shelves. Over the course of a single day a picker could walk as far as 24 kilometres (representatives from Amazon would frequently boast that the warehouse was the size of “10 soccer pitches”). We were paid the minimum wage to do this, which at the time was £7 ($9) per hour.

Before I started the job I had a relatively positive view of Amazon - admittedly derived from my use of the company’s website as a consumer. When I set out to write my book I was simply looking at low-paid, precarious work. I ended up working at Amazon by accident: my search for a low-paid job merely coincided with a recruitment drive on Amazon’s part.

Yet what I found while working for Amazon shocked me. I had done warehouse work previously when I was younger, along with a range of other poorly paid, manual jobs. In other words, my shock at the way workers were treated by Amazon was not a product of some wet-behind-the-ears naivety: I fully expected warehouse work to be tough. Yet what I witnessed at Amazon went far beyond that. This was a workplace environment in which decency, respect and dignity were absent.

The warehouse had the atmosphere of what I imagine a low-security prison would feel like. You had to pass in and out of gigantic airport-style security gates at the end of every shift and each time you went on break or needed to use the toilet. It could take as long as 10 or 15 minutes to pass through these gigantic metal scanners. A corporate, Orwellian form of double-speak was pervasive. You were not called a worker but an “associate”. You weren’t fired but instead you were “released”. Near the entrance to the warehouse, a cardboard cut-out of a fictional Amazon worker proclaimed, via a speech bubble attached to her head, that “we love coming to work and we miss it when we’re not here”.

The contrast between this sickly corporate uplift and the reality of life as an order picker at Amazon was stark. Workers were regularly admonished by management for clocking up so-called “idle time”, which was usually no more than the time it took to go to the bathroom. A recent survey of Amazon warehouse workers in England by the group Organise found that 74% were afraid to go to the toilet during a shift out of fear of missing productivity targets. On one occasion I found a Coca-Cola bottle containing urine sitting incongruently on a warehouse shelf amid the assorted miscellany, evidently left there by a worker too scared to take a toilet break.

Amazon operated a draconian disciplinary points system, whereby points were given to workers for things like missed productivity targets, “idle time” and clocking in a few minutes after the start of a shift. We were warned that talking to co-workers could also result in the acquisition of a point. Should you receive six points you would lose your job. Illness was punished as a misdemeanour by the company. I took a day off sick and was given a point for it – despite notifying Amazon several hours before the start of my shift that I was ill and offering to provide a note from the doctor. When I returned to work I asked an Amazon manager how they could justify such a policy, which effectively punished people for being ill. “It’s what Amazon have always done,” he replied blandly.

In Amazon’s case, convenience evidently has a cost, and this cost is borne by those toiling away in Amazon’s warehouses, rarely heard from in the media and invisible to the millions of people who every day submit orders through Amazon’s website. It’s about time these people – the labour we rely upon for our every whim – were given a voice, and Bernie Sanders deserves credit for giving them one.

• James Bloodworth is the author of Hired: Six Months Undercover in Low Wage Britain, published by Atlantic