Supermarkets have been warned they may be selling chicken past its use by date after the UK's biggest supplier was found in breach of food safety rules.

Workers at a factory run by 2 Sisters Food Group, which supplies thousands of supermarkets, were found to be changing the date chickens were killed to artificially extend their shelf life.

An undercover investigation by the Guardian and ITV News filmed workers mislabelling the slaughter date on poultry at the food plant - meaning supermarket packaging would carry the wrong sell-by dates.