Video footage from animal rights group shows workers kicking and throwing baby chicks and birds left to suffer and die.
An RSPCA investigation is underway after undercover researchers revealed shocking abuse of birds at two poultry farms on the Suffolk-Norfolk border.
The ill-treatment by workers at Brome Grange Farm and Tree Farm near Eye was captured on video by pressure group Animal Justice Project, which carried out a three-month surveillance operation earlier this year after it received a tip-off.
The animal rights campaigners filmed numerous harrowing scenes, which the group says was taken at both farms, including baby chicks being kicked, thrown and killed, and lame and dying birds being left to suffer and die.
The group also alleges chickens were left without natural light for weeks while food and water sources were left contaminated with sodden straw bedding.
Dismissed
The farms, which are close to each other, are rented by Free Range Chicken Ltd. The company's director, Harry Irwin, said he was "shocked and distressed by the footage".
He added: "Our number one priority is the highest possible animal welfare standards - this is the first incident of this nature in 16 years of business.
"Once alerted, we launched an urgent investigation to determine all the facts. "We have already suspended supply from these two farms until we are satisfied that welfare standards are at the high levels we demand, and members of the catching team involved have been dismissed."
Mr Irwin said a retraining programme for the farm staff and contractors had been launched across the farms and wider business "to ensure unacceptable instances such as this never happens again."
Suspended
Tree Farm was an RSPCA Assured farm - a certification that guarantees ethical treatment of animals - but was recently suspended from the scheme for breaching the standards.
In a statement the RSPCA said: "We are shocked and disgusted by the behaviour displayed towards these animals.
"We take all reports of animal cruelty and neglect extremely seriously and we are looking into these upsetting incidents. Our inspectors are liaising with a number of agencies."
Brome Grange Farm supplies chickens to Tesco but a spokesman for the supermarket said: "We have immediately suspended this farm while we fully investigate."
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