Heavy rainfall and low temperatures have seen Magners volumes in GB fall by 21.8% since March 1, with the figure exaggerated by the exceptionally hot weather in April 2011.
There was also a 21.5% fall in sales of the groupís Gaymer brands as net revenues in GB dropped 24.3%.
In a trading statement, C&C said: ďThe dip in consumption inevitably contributed to some overstocking in the supply chain and consequential pressure on retail pricing.†
ďThe percentage decline in the Magners brand also reflects a strong market share performance in the first quarter last year.†
ďLooking forward, levels of support and commercial activity around the brand will step up and we expect to see volume and revenue recover as the year progresses.Ē
Volumes in the Tennentís beer business in the UK were also down, by 6%.
C&C said: ďIn the off-trade, the marketís focus on value depressed overall brand volume in the period but the impact of improved pricing on the revenue line has been very positive.Ē