Horrifying footage reveals the squalid conditions endured by chickens at 'concentration camp' farms which supply eggs to supermarkets.

The film feature squawking hens packed into rows of cages in clips filmed as part of a year-long investigation by vegan charity Viva.

The enclosures were designed to give chickens more 'freedom' after smaller battery cages were banned in 2012.

But activists who visited farms across the UK - each of which was accredited with the British Lion Quality codes of practice - claim the conditions remain dire.

The film feature squawking hens packed into rows of cages in clips filmed as part of a year-long investigation by vegan charity Viva

One frame in the video features a hen with mangled skin and missing feathers (pictured)

They visited caged and free-range farms across the UK in 2015 and 2016 in an attempt to expose the conditions experienced by egg-laying hens.

It comes as farmers are forced to keep stocks of poultry birds inside to stop them catching avian flu, a restriction that has been in place since December 6.

Under EU rules they were allowed to continue labelling the meat and eggs as free-range until February 28.

However, after that date they were no longer permitted to do so, instead being labelled as coming from ‘barn-reared’ birds.

Supermarket giants including Tesco, ASDA, Morrisons, and Lidl pledged to stop selling eggs from caged hens - but not until 2025.

During filming at one farm, Julia Gellatley, Viva's founder and director, says: 'This place is like a concentration camp.

The shocking footage also shows young chicks on a conveyor belt in a unspecified factory

Shocking footage shows mangled corpses lying uncollected on the soiled floor among live birds (pictured)

'These so-called enrichment cages which are supposed to be better welfare are absolutely appalling.

'The cages are stacked one on top of another with these rows of them going on for how long? I don't know, maybe 200 metres (650 feet).'

Campaigners visited farms across England, ranging from the south coast to the north of the county.

At one farm, they claim they found up to 400,000 birds crammed in a single shed, and chickens had a postcard-sized plot of space in which to spread their wings.

Maggots gather around the lid of a large dustbin, containing the carcasses of dead chickens

Viva say they visited caged and free-range farms across the UK in 2015 and 2016 in an attempt to expose the conditions experienced by egg-laying hens

Shocking footage shows mangled corpses lying uncollected on the soiled floor among live birds, some of which have been left for so long they are just feather and bone.

Another clip shows birds having their beaks trimmed on a conveyor belt.

Piles of discarded, dead hens are heaped in a wheelie bin teeming with maggots at the same farm, while most birds at all sites had few feathers and mutilated beaks.

Evidence from 'free-range' sites shows chickens locked into equally cramped conditions - this time a dimly-lit stone shed, with not a blade of grass in sight.

Some farms were accredited under the RSPCA Assured Scheme, which is dedicated to farm animal welfare.

Activists, who visited farms across the UK claim the conditions remain dire at many facilities

Report author Claire Palmer said the investigation shows that regardless of the labels on boxes, eggs 'cause pain, ill-health and suffering on an unacceptable scale'.

She said: 'Four years on from the battery cage, 18 million hens remain incarcerated in cages, and those categorised as 'free-range' fare little better.

'Customers buying "higher-welfare" eggs may be unaware that they are funding the caging of hens by the very same companies.

'British consumers are being duped and we urge them to not support the cruelty by going vegan.'

Viva said mounting public pressure has resulted in a surge of cage-free pledges by supermarket giants like Tesco, Aldi, Asda, Morrisons, and Iceland.

But they said these bans will not come into force for another nine years, and called for them to be brought forward.