One of the largest suppliers of chicken to UK supermarkets has suspended operations after an investigation allegedly revealed a string of health and safety breaches.

2 Sisters Food Group (2SFG), which is headquartered in Birmingham and has factories across the region, said supply would only restart once it was satisfied workers had been "appropriately retrained".

An undercover reporter working at its West Bromwich site claimed to witness workers allegedly tampering with slaughter dates and mixing meat of different ages.

Source codes on crates of meat were also changed, the investigation by ITV News and The Guardian claimed.

The practices can artificially extend the shelf life of meat and make it untraceable in the event of an outbreak of food poisoning.

When meats of different ages were mixed together, the slaughter date of the newest batch rather than the oldest batch would be used, employees claimed.

2 Sisters food group probe after 'chicken slaughter dates changed'

Some workers also claimed the chicken that supermarkets rejected was sometimes repackaged at the factory and sent out again.

Quality assurance workers told journalists they were intimidated by production managers and worried about being sent home if they tried to enforce food hygiene rules.

2SFG said in a statement on Sunday: "We are shocked and distressed by the allegations and the footage which we saw for the first time on Thursday.

"Since the allegations were put to us by the Guardian and ITV, we have been working around the clock to get to the truth of the matter.

"We responded immediately by launching our own internal investigation at our West Bromwich plant and invited the Food Standards Agency (FSA) to independently review our standards.

"The FSA has been in daily attendance since the allegations were raised and confirmed that it has not identified any breaches.

"However, our internal investigation has shown some isolated instances of non-compliance with our own quality management systems.

"We have therefore decided to temporarily suspend operations at the site to allow us the time to retrain all colleagues including management in all food safety and quality management systems.

"All colleagues will remain on full pay and will attend site whilst training is undertaken. We will only recommence supply once we are satisfied our colleagues have been appropriately retrained.

"We continue to work closely with the FSA and our customers throughout this period.

"We remain committed to ensuring that we operate to the highest standards of hygiene and food safety and we act with honesty and integrity at all times."

On Sunday, Tesco became the latest supermarket to say it had decided to suspend buying chicken from the company, following Marks & Spencer, Aldi and Lidl.

2SFG was founded in 1993 and now produces one third of all of the poultry products consumed in the UK and had revenues of £3.1 billion in 2016.

Founder Ranjit Singh Boparan and his wife have built up a personal fortune of around £850 million, according to the 2017 Birmingham Post Rich List.

The company now has brands such as Fox's Biscuits, Goodfella's Pizza and the Harry Ramsden fish and chip chain in its stable, but poultry is still its strongest revenue stream.

The FSA said that it had found no evidence of breaches during an inspection of the plant.

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But it said it was still reviewing evidence, saying: "If any incidences of non-compliance are found we will take prompt and proportionate action with the business concerned, working closely with the local authority."

Meanwhile, Mr Boparan may be called to Westminster to face MPs over hygiene standards at his company, the Guardian reported.

The chairman of Parliament's environment, food and rural affairs committee, Neil Parish, said he wanted a "short, sharp inquiry" into practices at 2SFG.