A factory farm which supplies millions of eggs to supermarkets exposes its hens to "a life of extreme suffering", an animal rights group has said.
Hidden camera footage by Animal Equality appears to show birds at Walston Poultry Farm in Blandford, Dorset, with red raw skin living in cages stacked seven tiers high.
The farm also failed to carry out routine welfare inspections and left dead birds in cages, the group said.
The farm declined to comment.
Animal Equality placed concealed cameras at the site, which holds 500,000 hens, during five undercover visits over a six-week period.
It said one welfare inspection was seen during 96 hours of recording. Law dictates hens should be checked at least once every 24 hours.
The 140 million eggs produced at the factory each year are used to supply the Big & Fresh brand, which is owned by Noble Foods, and sold to several large supermarket chains.
Dr Toni Shephard, of Animal Equality, said: "We saw hens crammed into cages stacked seven tiers high.
"There were dead birds in cages. There were so many frail, featherless birds with red raw skin. There were tubs of dead birds sitting in the sheds, so really a life of extreme suffering."
A Noble Foods spokesman said: "We have immediately launched an internal investigation and audit of the site highlighted.
"Noble Foods remains committed and vigilant in demanding the highest standards from its suppliers."
Dorset County Council's Trading Standards confirmed it was investigating alongside the Animal and Plant Health Agency.