Food hygiene rules have been flouted at branches of two major UK supermarket chains, a BBC investigation has found.
The two BBC reporters worked undercover for several months
Undercover reporters from Whistleblower say customers were misled about freshness of food on the meat and fish counters at Sainsbury and Tesco stores.
Sainsbury said action was taken to address issues raised but safety had not been compromised.
Tesco said the film did not represent otherwise high standards and staff in the store concerned had been retrained.
Whistleblower reporter Audrey Brown applied for a job at a Sainsbury's store in Didcot, Oxfordshire, after receiving information from a former employee.
In one part of the programme, she is seen working on the meat counter where she identified products being sold a day after their sell-by date without customers' knowledge.
She was also told it was acceptable to shave the tops off some joints of meat to make them look fresher.
It is not illegal to sell food past its sell-by date, but it is store policy at both Sainsbury's and Tesco that once the food has passed that date it should not be sold to customers.
At Tesco, it is claimed such food was re-labelled and sold at a cheaper price and in one incident another undercover reporter is told to take some steaks that are past their sell-by date and mince them for sale.
At Sainsbury's, the BBC found deliveries would sometimes go astray and could not be unpacked quickly enough for them to be chilled in time.
Both companies issued statements in response to the programme's allegations.
Sainsbury's said: "We have identified some instances where our procedures had not been followed correctly at that store and have taken the necessary action to ensure these matters are addressed.
"Any local breakdown in procedure is entirely unrepresentative of the hard work and commitment to the high standards displayed every day by Sainsbury's store colleagues."
Tesco said: "We take allegations of this nature very seriously and, as a precaution, have retrained all counter staff in this store.
"Our customers should not be fooled into thinking that this programme has uncovered systematic failures or that the public is at risk."
Whistleblower: Supermarkets was broadcast on Tuesday 22 May at 9pm on BBC One and is available online for seven days from this page.
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