Britain’s supply of beer is at risk from the unseasonably hot weather, one of the UK’s biggest brewers has warned.

As the country basks in record-breaking temperatures for March, Molson Coors has revealed that a whopping 94% of arable farmers say the early sunshine is having a negative impact on barley yields. Just under half of barley farmers described the impact as “very profound”.

The brewing industry, which uses 1.7 million tonnes of UK barley every year, is concerned that the dry forecast for 2012 could mean a repeat of last year’s drought, which had a “major impact” on barley.

Hot weather can send nitrogen levels in barley rocketing which, according to Molson Coors global procurement head Graeme Hamilton, has a detrimental effect on its value for brewers as it means the barley contains less sugar, which reacts with yeast to make alcohol. That means brewers are forced to buy more barley to maintain abv levels and volume. There is also a risk that beer can turn cloudy - although that can be countered during the brewing process.

Last year, nitrogen content in barley hit record levels.

“We went into a dry spring last year, which slowed the development of the winter barley and caused the elevated nitrogen levels,” said Hamilton. “The UK is traditionally a net exporter of barley, but there was less available last year than in previous years.”