A factory inspection for the supermarket giant Tesco shows that a second chicken processing plant in the 2 Sisters Food Group was potentially breaching food regulations designed to protect consumers.

Leaked documents show that the supermarket's audit team gave a "red" warning to the Coupar Angus factory in Scotland after uncovering "major" issues of non-compliance in five different areas.

The report was part of a series of emergency inspections carried out by Tesco after ITV News and the Guardian uncovered problems at the 2 Sisters factory in West Bromwich, Site D, which lead to its temporary closure.

The results raise serious questions about how widespread bad practice was at 2 Sisters poultry operations. The company runs 12 chicken-processing plants and is the UK's largest supplier of supermarket chicken.

As part of our original undercover investigation at West Bromwich, we filmed several instances of chicken from the factory floor being thrown back onto the production line. We also recorded one instance of staff changing both the slaughter dates and the source codes on crates of meat.

The inspections by Tesco have not found evidence of either practice taking place elsewhere but at least one has revealed significant failures.

The audit at Coupar Angus raised concerns about "traceability" - an essential regulatory requirement, designed to protect the public. Meat processing companies are legally obliged to meticulously record when chicken is slaughtered, where it comes from and where it ends up.

During a two day long inspection at Coupar Angus, Tesco identified several occasions where that process appeared to have broken down:

We shared the findings of the audit with Professor Chris Elliott, the scientist who lead the inquiry into the horse-meat scandal.

Professor Elliott told us:

Tesco inspectors gave Coupar Angus the "red" rating after unearthing five compliance issues that it categorised as "major" - which the supermarket defines as "a deficiency which requires prompt attention to prevent a potential food safety failure or legal issue form arising".

Fewer than 1% of supplier sites receive a "red" rating during a Tesco audit - the worst score in the internal, colour-coded safety and quality compliance system which Tesco has devised.

ITV News understands that Coupar Angus was not the only 2 Sisters factory to be given a "red" warning by Tesco following our investigation.

In October the owner of 2 Sisters, Ranjit Singh Boparan, was summoned to appear before MPs as part of an inquiry triggered by our investigation.

He apologised for the problems at West Bromwich, insisted that his company had "high standards" and promised change. Mr Boparan also told MPs that parts of our original report had been misleading.

Mr Boparan declined our offer of an interview. In statement 2 Sisters Food Group said Tesco had carried out

"A standard inspection audit" at Coupar Angus and that "there is and never was any risk to food safety".

The statement added: "(The) issues (identified) were resolved with our customer two months ago."

A spokesperson for 2 Sisters insisted that the crates of meat that the auditors had failed to trace had not been dispatched to customers. The spokesperson also said that the factory computer had been relocated and made more secure.

Tesco declined our offer of an interview. In a statement the supermarket said:

Food regulations are designed to protect consumers. The Food Standards Agency is still investigating whether they were broken at 2 Sisters.

Tesco says it has shared the findings of its inspections with the FSA.

2 Sisters released on Tuesday details of audits and inspections at its chicken processing sites.