A business boycott of a production facility owned by the UK's largest supplier of supermarket chicken could have implications for two East Anglian processing plants.

2 Sisters Food Group is still in hot water after an undercover investigation claimed to have found breaches of food hygiene procedure at its processing plant in the West Midlands.

The group has production facilities in Thetford and Flixton, near Bungay, but neither were implicated in the investigation.

2 Sisters announced it was halting operations at the West Bromwich plant following an investigation by the Guardian and ITV which claimed to reveal tampering of the use-by dates on meat and poor food hygiene practises.

Following the allegations Tesco, Sainsbury's, Co-op, Marks & Spencer, Aldi and Lidl announced they would stop taking orders from the West Bromwich plant, known as Site D.

However none have said they would stop receiving supplies from other 2 Sisters processing facilities.

The Food Standards Agency (FSA), which has attended the plant in the days since the claims were published, said its inspectors had 'found no evidence of breaches', but that reviews of the evidence were continuing and 'if any incidences of non-compliance are found we will take prompt and proportionate action with the business concerned'.

FSA chairman Heather Hancock said: 'It is the responsibility of a food business to ensure that the food it sells is safe and what it says it is. We take any allegations of inaccurate labelling and breaches in hygiene regulations very seriously.'

In a statement 2 Sisters said it was 'shocked and distressed' by the allegations and the footage revealed by the Guardian and ITV on September 28.

It said its own investigations had uncovered 'some isolated instances of non-compliance' and that operations would be temporarily suspended at the West Bromwich plant while staff were retrained in 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 that our colleagues have been appropriately retrained. We continue to work closely with the FSA and our customers throughout this period,' it said.

A spokesman for Marks & Spencer said the company had commenced its own investigation into the allegations and would not be taking any more products from the West Bromwich site 'until that has been concluded to our satisfaction', but added that this would not affect other 2 Sisters sites supplying the company.

'The standards shown in the footage are unacceptable, we take hygiene and traceability very seriously and have extremely high production standards.

'The 2 Sisters site at West Bromwich supplied us with a selection of our range of fresh chicken portions. On Friday, we moved production of those lines to other sites that supply M&S,' he said.

A Sainsbury's spokesman said: 'All of our suppliers are expected to meet our high standards. We are concerned by these allegations and, while our investigation is ongoing, we have stopped taking any products from this site.'

A Co-op spokesman said the company had stopped taking supply of the one fresh chicken line which came from the West Midlands site, adding: 'Food safety and traceability throughout the supply chain is really very important for us and we have very high production standards which we expect our suppliers to meet. We will continue to work together with our supplier to make sure these high standards are always maintained.'

A Tesco spokesman said: 'We will not be taking any more chicken from the site until this has been addressed and all processes are carried out to the highest standard.'

They added that the firm's own investigations, supported by the FSA, had found 'no current evidence of breach of food safety procedures'.

The group's chief executive is Ranjit Singh Boparan, who also owns East Anglian turkey producer Bernard Matthews through a separate company.

The chairman of parliament's environment, food and rural affairs committee, Neil Parish, said on Friday he was preparing to call Mr Boparan to Westminster to answer questions about the allegations.