A poultry firm has launched an urgent investigation after campaigners released a video claiming to show chickens "deformed and dying" on East Anglian farms.

The footage was filmed by animal rights group Open Cages on four farms in Norfolk and Suffolk supplying the Cranswick chicken factory in Eye, near Diss.

Narrated by campaigner and TV presenter Chris Packham, the video shows chickens "completely or almost unable to walk", said the group, with many having "deformed and twisted legs".

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It also claims "blackened dead bodies were found rotting on multiple sites", while others had deep wounds and "hundreds were covered in filth and suffering chemical burns from laying in their own waste" in crowded conditions.

The group is campaigning against the intensive farming of poultry which it says is bred to grow "at an unnatural rate" to be slaughtered at 35 days old - birds which they have dubbed "FrankenChickens".

The Cranswick factory provides meat for Morrisons, and the campaigners have also accused the supermarket chain of hypocrisy over its claims to “take animal welfare seriously”.

Both Cranswick and Morrisons stressed the importance of animal welfare in all their operations, and the poultry producers said they have already launched an "urgent and thorough investigation."

Mr Packham said: "These images have revealed without any ambiguity that extreme suffering is rampant in the supermarket’s chicken supply chain.

"These poor animals are forced to endure pain, deformities, heart attacks and filthy, overcrowded conditions."

Open Cages chief executive Connor Jackson added: “It’s simple: 'FrankenChickens' are doomed from day one. You cannot sell them in your store, profit off their deformed, weak bodies, and then claim to take animal welfare seriously."

Eastern Daily Press: Animal rights campaigners Chris Packham and Open Cages have released a video claiming to show mistreatment of chickens being reared for Morrisons by poultry firm CranswickAnimal rights campaigners Chris Packham and Open Cages have released a video claiming to show mistreatment of chickens being reared for Morrisons by poultry firm Cranswick (Image: Open Cages)

A Cranswick spokesperson said: "Cranswick takes the welfare of chickens at our farms very seriously and it is always our first priority.

"After viewing this video footage we are now conducting an urgent and thorough investigation."

A Morrisons spokesperson said: "We care deeply about animal welfare throughout our supply chain and require all our suppliers to maintain the highest standards.

"We have asked Cranswick to conduct a full investigation and report back to us."

Eastern Daily Press: Animal rights campaigners Chris Packham and Open Cages have released a video claiming to show mistreatment of chickens being reared for Morrisons by poultry firm CranswickAnimal rights campaigners Chris Packham and Open Cages have released a video claiming to show mistreatment of chickens being reared for Morrisons by poultry firm Cranswick (Image: Open Cages)