Brewing giant Carlsberg-Tetley was forced to ship in emergency supplies of lager from abroad because of this summer's heatwave.

The company said yesterday the soaring temperatures in the past two months had led to a 40 per cent increase in sales across Britain as drinkers sought to quench their thirst.

Workers at Carlsberg-Tetley's plant off London Road, Northampton, struggled to cope with demand and called for extra supplies and lager vats from the firm's head office in Denmark.

Spokeswoman Donna Cresswell called the demand "unprecendented".

She said: "We've seen a huge increase in the amount of lager sold during the heatwave."

"Everybody has been working flat out to meet demand but we've also had to call over to Copenhagen to get them to ship some extra supplies in."

Supermarket chain Tesco said beer sales were up 55 per cent, with one million more cases of lager and bitter sold last weekend compared with 12 months ago.

Sainsbury's said sales of lager this month were up 50 per cent on last year and it expected to sell 14 million cans and bottles this week alone.