Real ale, the perennially moribund segment of the UK beer market, is making a comeback. For the first time in half a century, a drink that appeared to be in terminal decline is increasing its share – at the expense of its upstart continental rival, lager.

The drink's renaissance will be confirmed this week with the publication of the new edition of the Good Beer Guide, which will reveal there are now more than 700 real ale brewers in the UK, the highest number since the second world war and four times as many as in 1971, when the Campaign for Real Ale (Camra) was founded in a last-ditch effort to save the beverage from oblivion.

According to figures released by the British Beer and Pub Association, ale's share of the £17bn UK beer market rose to 20.6% last year, up from 20.4% in 2008. The popularity of real, or cask, ales – non-carbonated beer made with traditional ingredients – has been key to the increase. Real ale's share of the draught beer market – served in pubs and clubs – rose from 5.8% in 2008 to 6.1% last year, the first increase for generations.

Conversely, lager's share of the beer market fell from 74.5% in 2008 to 74.3%, arresting half a century of continuous growth, which suggests that British drinkers' love affair with carbonated beers may finally have peaked.

Iain Loe, a spokesman for Camra, said drinkers were returning to real ale because of its moderate strength – often under 4% – compared with stronger lagers that are usually above 5%. "Real ale is a naturally refreshing drink; people are realising it is healthier than other types of alcohol," Loe said.

Many real ale brands have tapped into consumer demand for greener, more local products, according to drinks analysts. Julian Grocock, chief executive of Siba, the Society of Independent Brewers, said its 420-plus members had seen their combined sales rise 4% in 2009 compared with the previous year.

Significantly, Siba's smaller members, who each brew fewer than 350 barrels a week and constitute the vast majority of its membership, saw volume sales rise by 8.5%, an impressive achievement in the jaws of a recession.

"A lot of our members are professional brewers who have worked for the big brewers and have now set up their own business," said Grocock, whose organisation had only 20 members in 1980. "They are brewing all sorts of beers; we are not just talking about bitter and mild, but stouts and porters, wheat beers, heather beers up in Scotland. There's now a huge variety out there."

Real ale's renaissance owes much to a decision taken in 2002 by the then chancellor, Gordon Brown, to give 50% tax relief to the smallest beer producers.

Supermarkets have also played a part. Tesco now stocks 350 bottled ales, compared with 20 in 2005. It is estimated that there are between 1,500 and 1,800 bottled ales on sale in off-licences across the UK. Figures from Kantar Worldpanel, a firm of independent retail analysts, show that shop sales of real ale rose by 7.2% last year, while lager sales fell by 4%.

"The growth in popularity of real ale in the last few years has been spectacular, with the greatest accolade being that it has started to achieve its holy grail of winning over a younger audience," said Ian Targett, Tesco's ale buying manager. "Much of that is due to its increasing use as an accompaniment to food."

The proportion of women who have tried real ale has doubled from 16% in 2008 to 32% this year, according to Camra. The proportion of 25-to-34-year-olds who have tasted real ale rose over the same period from 28% to 50%. "Real ale used to have a very traditional appeal," said Paul Halsey, managing director of the Warwickshire-based Purity Brewing Company, which started five years ago and now supplies Tesco. "The marketing is a lot better now, much cooler and cleaner, so people in their 20s and 30s have more of an interest in it."

Camra said it hoped that real ale might now help pubs fight back. "The pub is one of the few places where you can drink real ale," Loe said. "It's still a relatively cheap night out."

Additional reporting by Cate Attwood