The speed at which milk has started to sour in fridges this summer has become a social media discussion point, with people complaining of dairy products going bad before their use-by dates.

Many have complained that milk, of various brands and bought from different retailers, is souring within three days of being opened, despite being kept properly chilled. Some expressed concern that the use-by dates had been pushed out to extend shelf life.

However, retailers and the Irish Dairy Council insist the natural shelf-life of milk is normally in excess of one week and has not been extended.

“There is no reason for normal pasteurised milk to go off more quickly during the warm weather spell as long as it is stored at the right temperature,” a spokeswoman for the Irish Dairy Council said.

She suggested consumers check the temperature of their fridge to ensure the “dial on their fridge was not moved during cleaning or when stacking food; or that the temperature is functioning correctly”.

According to the Food Safety Authority of Ireland, the thermostat should be set at a temperature that will ensure the temperature of the food is 0-5 degrees. Milk should not be stored in the door of fridges, where the temperature fluctuates. "People need to remember that the chill chain extends from the supplier to the home. Shoppers who keep their milk in the boot of the car for a couple of hours break that chain, particularly in hot weather,"said the dairy council spokeswoman.