Facebook has said it remains committed to ensuring that the contractors who moderate its sites are treated fairly and with respect by their employers, after a report revealed the traumatic experiences of many of the low-paid workers who keep violence, hate speech and sexual imagery off its platforms.

The vast majority of the more than 15,000 people who work as Facebook moderators are employed by third-party contractors, and their working conditions are often far from the stereotype of a perk-filled Silicon Valley job.

According to a report in the Verge, Facebook moderators at one contractor are paid $15 an hour and work in conditions more like a call centre than the frontline of a $500bn company.

They get short, rigorously enforced breaks, leading to long queues in tiny bathrooms; oppressive oversight of workrate and accuracy leaves workers feeling under pressure to spend no more than 30 seconds on each item and to moderate hundreds every day without getting more than one in 20 wrong; and they are barred for security reasons for carrying any phones, pieces of paper or even gum wrappers into the office, it is claimed.

Moderators also told the Verge they were developing “PTSD-like symptoms” owing to the nature of some of the work, which can involve watching graphic violent or sexual content in order to make a decision about the correct reason for removing it.

Some said they coped by sharing dark jokes about suicide and getting high in breaks, and some had been caught having sex in the stairwells. One said the enforced secrecy forged closer ties: “If you’re not allowed to talk to your friends or family about your job, that’s going to create some distance. You might feel closer to these people. It feels like an emotional connection, when in reality you’re just trauma bonding.”

Other employees said colleagues had come to believe the conspiracy theories they were supposed to be flagging. A former employee told the Verge: “I no longer believe 9/11 was a terrorist attack”; another reportedly promotes the idea that Earth is flat, while a third “has begun to question certain aspects of the Holocaust”, the website reports.

Staff are allowed two nine-minute “wellness breaks” each day if they need to walk away from the work. But some reported not being allowed to use those breaks to go to the toilet – even if they hadn’t had a chance to do so during their formal breaks.

In response to the report, Facebook said it worked to ensure that its contracts with third parties “explicitly require good facilities, wellness breaks for employees and resiliency support”, and said it needed the help of the external contractors given the speed with which it had grown its moderation team.

Justin Osofsky, Facebook’s vice-president of global operations, said: “These partnerships are important because they allow us to work with established companies who have a core competency in this type of work and who are able to help us ramp with location and language support quickly. They have experience managing large workforces; scaling quickly for new issues and risks; and adapting with us as the risks to our community and product needs change over time.”

Osofsky said the company encouraged “partner employees” – those workers employed by third-party contractors – to raise concerns with their employers’ HR teams or to call a dedicated whistleblower hotline that the company had set up for this purpose.

“Put simply, after a couple of years of very rapid growth, we’re now further upgrading our work in this area to continue to operate effectively and improve at this size,” he said.