Milk bottle labels will change colour to warn people if their fridge is too warm under a new trial to reduce the amount which goes sour and gets tipped down the sink.

The colour-changing labels will start appearing on supermarket bottles from next year, according to waste reduction charity Wrap, which is developing them with retailers and dairies.

The so-called "thermochronic" labels, which contain heat sensitive ink, are being developed after Wrap conducted research concluding that households are throwing away £25 million of unconsumed milk a year, which goes off while sitting in the fridge.

The most common reason for unnecessary milk waste are warm fridges, Wrap said. Typical fridges in UK homes are operating at 2°C warmer than the temperature recommended by the Food Standards Agency guideline of between 0-5 degrees, it is claimed.