Tim McKinney spent around two months working at Amazon’s distribution centre in Dunfermline over Christmas 2013. The 61-year-old street pastor, who is originally from Arizona in America but now lives in Fife, wanted to go ‘undercover’ at Amazon after hearing about conditions there, as well as to earn some money to support his evangelism.

He said he was “shocked” at what he experienced while working there and said he found a culture of fear and intimidation and staff being treated like “cattle”.

He said: “I had heard different things and people complaining about it – so when I heard they were hiring for the Christmas break I thought it would be a good fill-in and a good chance for me to see what I had been hearing so much about, particularly with it being an American company.

“I was shocked and really upset when I began to see the things I began to see. The working conditions were basically people being treated as cattle.

He added: “I asked a couple of guys how do you make it here. They told me you watch your back and keep your head down. There was a lot of intimidation and a lot of fear.”

McKinney said there was one occasion when he was talking to one of the line supervisors when he saw “fear in his eyes”.

“I looked around and there was his boss walking down the walkway above him,” he said. “It was like you would have seen a deer in car headlights. He froze and then ran – and this was a grown man who had been there for a while.

“They would rather put up with anything than lose their job – as there were plenty of people to take their place.”

McKinney, who mainly worked as a packer during his time there, said he also found a number of issues with working conditions – including poor quality safety shoes which were mandatory while he worked there and a lack of ventilation. He said: “My feet were killing me walking and I had to come home and prop them up just to get the blood flow going.

“I talked to people who had been there for a while and they said they had been putting up with this for years. In the men’s toilet someone had even scribbled 'My feet – RIP', like on a headstone.

“A lot of people were taking antibiotics and painkillers and there were guys I spoke to who had worked there for a couple of years and they said we don’t even feel our feet anymore.

“One guy I saw walked like an old, old man. He shuffled, that is how bad he was.”

He added: “It was also extremely hot – there would be snow outside, almost blizzard conditions. You would just be sweating as there was no ventilation.”

McKinney said he refused to be intimidated by the working conditions and target-driven culture and used humour to try to get his point across.

“There were many times the line was broken down and you were standing there twiddling your thumbs. I teased the line supervisors saying how can we keep up with our targets?,” he said, “They didn’t say anything as they were afraid of losing their job.

“I think it would do better with a union – but that was a dirty word if you discussed that. I would joke when is the next meeting of the ‘United Scottish Packers Union’ – the response was don’t say that, it will get you fired.”

Amazon declined to comment on McKinney’s claims, saying it did could comment on individual cases.