Chickens crammed into “dirty and overcrowded” sheds resorted to cannibalism, and many suffered ammonia burns, investigators said.
Viva !, the charity which secretly filmed at the three locations, says factory farms create disease-ridden land.
Tesco says he immediately launched an investigation when he learned of the results.
All three sites have been approved by Red Tractor, which claims to guarantee that the animals have been well cared for.
But an expert described the scenes as “very disturbing”, with animals “clearly in pain”.
Producers all use selectively bred birds to gain unusually rapid weight – a common practice in chicken farming to maximize sales.
At a Herefordshire poultry company, which supplies Avara Foods, Tesco’s largest supplier of poultry meat, the vegan charity said 30,000 birds crammed into one of the 15 sheds were jostling on top of each other to find space.
The videos showed birds collapsing because their legs were too weak to hold their “grotesquely overweight” bodies. This meant that they could not access food or water points, causing death from starvation or dehydration, it was claimed.
“The damning footage also shows dead birds being trampled into the ground and covered in rubbish, which appear to have been left for some time – not surprisingly given the large number of birds in the shed,” said a spokeswoman.
Chickens raised to grow intensely and quickly are known to suffer from heart attacks, fractures and difficulty breathing.
At a Somerset poultry farm, which works for Hook 2 Sisters, investigators said they found “many dead and decaying birds”.
Many had painful “shank” burns from the ammonia on the floor.
Investigators reportedly discovered that other birds were collapsing and panting heavily.
Food group 2 Sisters, whose customers include Aldi, the cooperative, KFC, Lidl, Sainsbury and Tesco, says it produces around a third of all poultry products consumed in the UK.
On a Derbyshire farm under contract to Moy Park, which sells chicken to Tesco and Sainsbury, footage showed “countless dead birds, left to rot among the living”.
A large number of the chickens appeared to have lost feathers after being pecked, which would be a sign of frustration among the birds.
Moy Park is owned by Pilgrim’s Pride, an American company majority-owned by Brazilian meat giant JBS, which has been linked to Amazon deforestation.
Andrew Knight, Veterinary Professor of Animal Welfare, said: “These investigative images are very disturbing and the animals are clearly suffering on these farms.
“I am concerned to see examples of cannibalism, feather pecking and birds suffering from severe feather loss. “
Viva! Investigator Lex Rigby said, “Our insatiable desire for cheap chicken has led to an alarming increase in American-style mega-farms that prioritize profit over welfare.
“Vast factory farming facilities litter the countryside, causing unnecessary pain and suffering, while damaging our health and the environment.
“Marketing tricks consumers into believing the UK has some of the highest animal welfare standards in the world, but the reality is far from the advertisements. “
The farms are considered to meet industry standards, she said.
The vast majority of chicken in UK supermarkets comes from 2 Sisters, Moy Park and Avara Foods.
A Tesco spokesperson said: “We require all of our suppliers to meet high animal welfare standards. Any complaint from suppliers falling below these criteria is unacceptable. We immediately began an investigation of these farms as soon as we became aware of the allegations.
“Independent audits of the three farms revealed that the assurance system and legislative requirements were met at the time of the inspection, but we will continue to monitor the situation closely and further audits will be carried out. “
A spokesperson for Sainsbury’s said the supermarket is committed to high welfare standards and regularly reviews all of its locations.
Lidl said it is committed to building on its high welfare standards, adding: “All of our chickens meet nationally recognized standards including Red Tractor Assured, RSPCA certification and farmers and organic producers. Strict controls are in place on how birds are handled and cared for, with compliance ensured through regular audits. The chain said it was working with suppliers to ensure continued progress.
A spokesperson for Moy Park said the company has no tolerance for anything that endangers the health and well-being of birds, and has conducted a thorough investigation into the reception of the images. , adding: -standards of well-being.
They closely monitor welfare conditions on farms to ensure the highest standards are met, they said.
A spokesperson for Red Tractor said, “Protecting the health and welfare of animals is a top priority. As soon as we became aware of the images, an investigation was launched to verify if they presented an accurate representation of the management of the farms and the implementation of our standards. All sites were found to be well managed and up to our program standards.
Avara said in a statement, “The welfare of the animals in our care is of the utmost importance to us and our customers. After reading these images, we carried out a one-off audit of the farm in question, just like Red Tractor. We were absolutely pleased with the level of bird welfare evident on the farm and Red Tractor found no major issues. “
A spokesperson added that the sick and lame birds had not been identified during the filming of the film because it was shot at night, and they were reportedly found in the morning.
He said it was “reckless” of investigators to visit the property during the lockdown and an outbreak of bird flu.
Andrew Opie, Head of Food and Sustainability at the British Retail Consortium, said: “Our members take their animal welfare responsibilities very seriously and work closely with trusted suppliers to ensure standards high levels of well-being are respected. They have strict processes in place and will immediately investigate any allegations and take appropriate action. “
A spokesperson for Hook 2 Sisters said, “We abhor all reports of animal suffering and condemn any violation of the high standards we expect from everyone.
“In this case, the allegations are false. This farm has been inspected by eight independent audit bodies, and a recent report from a veterinarian confirms that no concerns were reported at any time, including Red Tractor’s last audit on July 22.
The independent also asked other brands for comment.