Animal activists have broken into a Northland chicken farm to expose what they've described as "disgusting" and "heartbreaking" conditions.
The Whangarei farm is owned by Mainland Poultry, which is currently trying to open a new mega facility in the Waikato.
Footage captured by Direct Animal Action activists shows decomposing chicken carcasses on the ground and mice running through cages.
"We knew we wouldn't be given permission to go to the farm so we went, one evening, after business hours, walked through a door and started filming," Activist Deirdre Sims said.
What they filmed is disturbing.
"It never ceases to shock me the extent humans will go to in pursuit of a cheap egg," Ms Sims said.
DAA launched their covert investigation in response to plans by Mainland Poultry to open a mega farm in the Waikato.
The new facility would house 600 thousand laying hens and 200 hundred thousand rearing birds.
"We've had information that it's going to be colony cages and a new type of intensive system called aviary, which is a mutli-tiered, intensive system," Ms Sims said.
In a statement, a Mainland Poultry spokesperson said they were extremely concerned by the conditions revealed in the footage.
They said it was unacceptable, and not reflective of their animal welfare practices or operational standards.
They also said, while the footage was obtained illegally - in the dead of night - they're grateful it was brought to their attention.
The company has launched an investigation and says immediate corrective action will be taken.