Protesters dressed as butchers have targeted Morrisons stores across the country, accusing the supermarket of sourcing most of its chicken meat from intensively farmed poultry.
Animal welfare campaigners from Open Cages and The Humane League UK descended on nearly 20 Morrisons supermarkets, including branches in Glasgow, Bradford and West Sussex.
They held up billboards and displayed deformed “Frankenchicken” images, demanding their removal from the retailer’s shelves.
Open Cages claimed the supermarket continued to source the vast majority of its chicken meat from birds genetically engineered to grow 400% faster than normal.
Morrisons said all its regular chicken is raised to above Red Tractor standards and it actively monitors for any malpractice in its supply chain.
Last year, undercover filming found chickens collapsing in their waste on four farms supplying Morrisons’ welfare-assured Butcher’s on Market Street meat label.
Connor Jackson, CEO of Open Cages, said: “Around 30% of Frankenchickens can barely walk because they can't handle the immense weight.
“Millions of these monstrous birds die from heart attacks because they can’t handle growing 4x faster than natural, millions more have their necks broken to simply put them out of their misery."
Morrisons has said that procedures are now in place to “significantly reduce” the chances of the problems in the footage happening in the future.
Over 300 companies across the UK and Europe have signed the Better Chicken Commitment (BCC), meaning that by 2026 they will sell only slower-growing chickens reared with far more living space.
Sainsbury's recently pledged to stop sourcing chickens from overcrowded conditions for all own-brand meat by 2023.
Open Cages added M&S, Waitrose, KFC and Subway were among hundreds of companies to have already pledged to stop selling "Frankenchickens".
Morrisons said it had committed to offering a range of chicken adhering to all nine of the BCC standards.
A Morrisons spokeswoman added: "We care deeply about animal welfare.
“All our regular chicken is raised to above Red Tractor standards; we are also the only retailer in Europe to ask our fresh chicken suppliers to require chicken to be born into the barn in which it will be raised by 2025.
“80% of our fresh chicken meets this standard already. We also actively monitor for any malpractice in our supply chain; we will never tolerate it or look the other way and if we ever find it, we will act swiftly and decisively."
A recent YouGov poll found that 78% of Brits oppose the use of farming practices which cause animals to suffer in order to produce cheap food. A majority strongly opposes them.