A three-month investigation by the Animal Justice Project uncovered examples of alleged animal abuse at Trees Farm and Brome Grange in Suffolk.
Investigators said farm workers left lame or dying birds to suffer for days, despite workers carrying out daily “welfare checks” in the sheds where the chickens were kept.
At one point, a worker allegedly urinated into a bucket before throwing seriously injured birds into it eight hours later.
The Animal Justice Project said the footage shows the suffering of so-called “high welfare” chickens who are raised for meat production.
While working undercover between February and May, investigators said they witnessed nearly 500 chicks dying in their first week at one farm, with some birds having their necks broken by farm workers who threw them onto the ground to die.
One chick was allegedly recorded as being left for eight hours to die.
The investigators also found a "dilapidated, sparse and large concrete 'range' for 'free-range' birds" which breached RSPCA guidelines.
Campaigners are now demanding the RSPCA prosecute individuals whose actions breached animal safety standards, after the organisation suspended one farm from its accreditation scheme.
The Animal Justice Project claimed workers' actions breached RSPCA standards and EU laws, including Council Directive 2007/43/CE and Council Regulation 1/2005 on the Protection of Animals during Transport and Related Operations.
The group's findings were submitted to the Animal Health and Protection Agency (APHA) and Red Tractor, who have since suspended both farms “with immediate effect”.
A spokesperson for the RSPCA said the organisation was “shocked and disgusted by the footage.”
"It is completely unacceptable for animals to be treated this way and we understand why you are so upset. It deeply saddens us that one of the farms in the footage is RSPCA Assured certified [Trees Farm],” they said.
"We have visited the farm and suspended it, along with the catching team, from the scheme for breaching our standards. The other farm [Brome Grange] has not been a member of RSPCA Assured since January 2018.
"We have also passed the information on to the RSPCA Inspectorate who are liaising with a number of agencies about these serious concerns."
Tesco said it has suspended Brome Grange Farm while it investigates the footage.
The Animal Justice Project will take their findings to the Annual National Poultry and Egg Awards in July to protest the poultry industry.
Claire Palmer, the group’s founder, claimed the public is “being fed a lie by the industry and RSPCA” over the treatment of so-called high welfare chickens.
"This extensive investigation into the lives of 'slow growing' and supposedly high welfare chickens - from the placing of chicks to the catching of young birds at nine weeks old for slaughter - reveals that 'meat' chickens are subjected to cruel abuse, pain and suffering regardless of labels,” she said.
"Animal Justice Project advocates a vegan diet for consumers as the only solution to truly protect animals."
In response to the investigation, Free Range Chicken Ltd, who run both farms, told The Daily Mail: "We have suspended supply from these two farms until we are satisfied that welfare standards are at the high levels we demand and members of the catching team involved have been dismissed."
Agencies contributed to this report
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