Budding singers who impressed the judges in their original auditions were invited to London last week for the competition's second round, which sees the lineup whittled down to 24 each year.
However, an 18-year-old contestant named Lisa walked off the programme before the six-day process was over, claiming that producers treated aspiring stars poorly.
The girl, who refused to give her full name, told The People: "The lowly-looking meat on our plates had been treated with more humanity than us."
It is believed that the wannabe popstars were required for daily filming at the Hammersmith Apollo concert venue in west London before sleeping in £125-per-night rooms at the Hammersmith Novotel.
Lisa added: "I thought boot camp would be a good experience but it's like a concentration camp where the producers are your jailers. They made us sit in the holding room for hours, sometimes eight, while they filmed. You weren't allowed to rehearse, there was no TV, you couldn't talk. They even took your jewellery if it was too noisy."
Meanwhile, a contestant in the 'over 25s' category complained: "On the days you weren't auditioning, you would be sat in the audience at the Apollo. You were allowed two loo breaks all day, only when the judges weren't there."
It is not the first time that contestants have criticised producers for their behaviour at boot camp. In 2007, Joy Philippou, then 79, described the experience as "really scary". Her complaints were later backed by fellow auditionees Kim Marrero and Natasha Benjamin.
Responding to the latest claims, an X Factor source insisted: "Yes, it was long hours but they knew what they were signing up for. The hopefuls got breakfast at the hotel and decent food throughout the day."