Chickens died of thirst and dead birds left to rot at suppliers to Tesco, Sainsbury, Lidl and KFC

Severely disabled birds died of thirst, while carcasses were left to rot among the living at the UK’s three largest poultry producers, according to an investigation by a vegan charity. The producers supply top brands including Tesco, Sainsbury, Lidl and KFC.

Chickens crammed into “filthy, overcrowded” sheds resorted to cannibalism, and many suffered ammonia burns, investigators say.

Viva!, the charity that secretly filmed at the three sites, says factory farms create breeding grounds for disease.

Tesco says it immediately launched an investigation when it learnt of the findings.

The three sites were all approved by Red Tractor, which says it guarantees animals have been well cared for.

But one expert described the scenes as “highly disturbing”, with animals “clearly suffering”.

The producers all use birds selectively bred to gain weight unnaturally quickly – a common practice in chicken farming to maximise numbers sold.

At a poultry company in Herefordshire, which supplies Avara Foods, Tesco’s biggest poultry meat supplier, the vegan charity said 30,000 birds crammed into one of 15 sheds were scrambling over each other to find space.

The videos showed birds collapsing because their legs were too weak to hold their “grotesquely overweight” bodies. It meant they could not access food or water points, causing death from starvation or dehydration, it was claimed.

“The damning footage also shows dead birds trodden into the ground and covered with litter, which appear to have been left for some time – which is unsurprising given the sheer number of birds in the shed,” a spokeswoman said.

Chickens bred to grow intensely rapidly are known to suffer heart attacks, broken bones and breathing difficulties.

Sick or injured birds were not humanely culled in line with government guidelines, the investigators claimed.

At a poultry farm in Somerset, which works for Hook 2 Sisters, investigators said they discovered “numerous dead and decaying birds”.

Many had painful “hock” burns caused by ammonia on the floor.

Investigators reportedly discovered other birds collapsed and panting heavily.

The 2 Sisters food group, whose customers include Aldi, the Co-op, KFC, Lidl, Sainsbury and Tesco, says it produces around a third of all poultry products eaten in the UK.

At a Derbyshire farm under contract to Moy Park, which sells chicken to Tesco and Sainsbury, footage showed “countless dead birds, left to rot amongst the living”.

A high number of chickens appeared to have lost feathers from being pecked at - said to be a sign of frustration in 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, a veterinary professor of animal welfare, said: “This investigation footage is highly disturbing, and animals are clearly suffering on these farms.

“I am concerned to see examples of cannibalism, feather-pecking and birds suffering severe feather loss.”

Viva!’s head of investigations Lex Rigby said: “Our insatiable desire for cheap chicken has led to an alarming rise in US-style mega-farms that prioritise profit over welfare.

“Vast industrial rearing facilities litter the countryside, causing unnecessary pain and suffering, as well as damaging our health and the environment.

“Marketing leads consumers to believe the UK has some of the world’s highest animal-welfare standards but the reality is a far cry from the adverts.”

The farms are considered industry-standard, she said.

The vast majority of UK supermarket chicken comes from 2 Sisters, Moy Park and Avara Foods.

A Tesco spokesperson said: “We require all our suppliers to uphold high animal-welfare standards. Any claims of suppliers falling below these are unacceptable. We immediately began an investigation of these farms as soon as we were made aware of the allegations.

“Independent audits of the three farms found that assurance scheme and legislative requirements were being met at the time of inspection, but we will continue to monitor the situation closely and further audits will be carried out.”

A Sainsbury’s spokeswoman said the supermarket was committed to high welfare standards and regularly reviewed all of its sites.

Lidl said it was committed to building on its high welfare standards, adding: “All our chicken complies with nationally recognised standards, including Red Tractor Assured, RSPCA certification and Organic Farmers and Growers. There are strict controls in place on how birds are handled and cared for, with compliance ensured through regular audits.” The chain said it worked with suppliers to ensure continued progress.

A Moy Park spokesperson said the company had zero tolerance of anything that jeopardised birds’ health and welfare, and it carried out a thorough investigation on receiving the footage, adding: “The farm was independently audited immediately and was certified as fully compliant with all animal-welfare standards.”

They closely monitor welfare conditions on farms to ensure the highest standards are adhered to, they said.

A Red Tractor spokesperson said: “Protecting animal health and welfare is a top priority. As soon as we were made aware of the footage, an investigation was launched to substantiate whether they presented an accurate representation of the farms’ management and implementation of our standards. All sites were found to be well managed and compliant with our scheme standards.”

Avara said in a statement: “The welfare of the animals in our care is of the highest importance to both us and our customers. After being made aware of this footage, we undertook a spot audit of the farm in question, as did Red Tractor. We were absolutely satisfied with the standard of bird welfare evident on the farm and Red Tractor found no major issues of concern.”

A spokesman added that sick and lame birds had not been identified when the film was shot because it was done at night, and they would have been found in the morning.

He said it was “reckless” of the investigators to go onto the property during lockdown and a bird flu epidemic.

Andrew Opie, head of food and sustainability at the British Retail Consortium, said: “Our members take their responsibilities to animal welfare very seriously and work closely with trusted suppliers so that high welfare standards are upheld. They have strict processes in place, and will immediately investigate any allegations and take necessary actions.”

A Hook 2 Sisters spokesman said: “We abhor any reports of animal suffering and condemn any breaches of the high standards we expect everybody to uphold.

“In this case, the allegations are untrue. This farm has been inspected by eight independent auditing bodies, and a recent veterinary surgeon’s report confirms no concerns have been highlighted at any point, including the last Red Tractor audit on July 22.”

The Independent also asked the other brands to comment.