The new report, entitled 'No Relief', is based on three years of research, and interviews with current and former poultry workers, attorneys, medical experts and worker advocates.

It alleges that poultry processing workers' bathroom breaks are inadequate, particularly for women; that workers are mocked, ignored or threatened with firing for asking for breaks; and that workers sometimes limit food and drink consumption to unhealthy levels to cope.

“I was stunned when poultry workers in Arkansas told me that people regularly wear diapers to work in the plants. They feel they have to put up with this, to keep their jobs,” said Minor Sinclair, Director of Oxfam America’s US Programme, in a statement.

Oxfam America called for immediate improvements to worker conditions, particularly at Tyson Foods, Pilgrim’s, Perdue, and Sanderson Farms, which cover nearly 60 per cent of the poultry market in the US.

Health and safety of employees a 'top priority'

The National Chicken Council and the US Poultry & Egg Association released a joint statement in response, saying: “The health, safety and respect of our employees is very important, and we value their contributions in helping to produce our food.

"We’re troubled by these claims but also question this group’s efforts to paint the whole industry with a broad brush based on a handful of anonymous claims. We believe such instances are extremely rare and that US poultry companies work hard to prevent them.

"Although individual practices vary by company, restroom breaks are planned for any production line.

"Most facilities also employ extra people to cover for production workers who request a bathroom break. In addition, medical-related situations are taken into account and accommodations are made.

"Coordinating restroom breaks in the workplace is certainly not unique to the chicken industry. Whether it’s a cashier, bus driver, bartender, bank teller or just about any manufacturing job, there are practices in place related to restroom breaks that are clearly outlined to the employee.”

In Oxfam's report, Tyson Foods responded to the allegations by saying: "Restroom breaks are not restricted to scheduled work breaks and can be taken at any time. Our production supervisors are instructed to allow Team Members to leave the production line if they need to use the restroom. Not permitting them to do so is simply not tolerated.

Tyson continued: "As reported in our new sustainability report, a third-party company is already involved in assessing working conditions in our plants."

Perdue commented: "“The health and welfare of our associates is paramount and we take these types of allegations very seriously. The anecdotes reported are not consistent with Perdue’s policies and practices. Unfortunately, we do not have enough information to investigate the validity of these complaints."

Perdue also said that employees had the option to make their voices heard by calling an anonymous hotline, as part of the company's 'Open Door Policy'.