The global advertising industry will rely increasingly heavily on China for growth next year, according to a study predicting that the surge in investment by multinational brands will continue even after this summer’s Olympics.

The Beijing Games are expected to boost the world’s third-largest advertising market by 22 per cent to $35bn this year.

And the study from GroupM, the media arm of Sir Martin Sorrell’s WPP marketing conglomerate, predicted almost the same growth in 2009, with a 19.5 per cent increase in spending.

The figures are below growth rates earlier in the decade but an increase over the 18.3 per cent increase in media spending witnessed in 1997, when many global ­marketers held back spending in anticipation of the Olympics, according to Adam Smith, futures director for GroupM.

With a slowdown already visible in US and western European advertising markets, China will account for 23 per cent of the 5.8 per cent rise in global ad spend GroupM expects this year, rising to 30 per cent of the 4.5 per cent global growth it forecasts for next year.

Television and the internet are driving the growth in marketing investment in China, with state broadcaster China Central Television alone expected to make almost $400m in advertising sales from broadcasting the Olympics, or 6 per cent of all new media investment in the country this year.

About 90 per cent of China’s 1.3bn people have access to a television, and CCTV secured a record share of between 63 per cent and 69 per cent of China’s television audience for last week’s opening ceremony.

GroupM cautioned that rising demand and a limited supply of airtime means television has become “a sellers’ medium, in which the big channels like CCTV, Beijing TV and Shanghai Media Group have tremendous power” over pricing.

CCTV controls more than one third of national advertising, GroupM estimates, and secured an 18 per cent increase in advertising pricing at last November’s annual auction for prime slots.

Overall, advertisers face inflation of about 20 per cent in media costs on Chinese television this year, as they aim to cut through the “rising clutter” of brands pouring into the Chinese market.

The challenge of getting messages across is especially acute this year, Group M found, posing “a major dilemma” for brands that are not among the Olympic sponsors.

“Advertisers entering this market will pay big premiums but may still be crowded out by large multinational sponsoring brands and being lost among the 60-plus sponsors,” the report concluded, adding that such brands might be better waiting until after the Olympic period to invest.

Having overtaken Germany as the world’s third- largest advertising market in 2007, China is due to pass Japan in two years.

The growing spending power of Chinese consumers is driving the interest from marketers, led by pharmaceutical, healthcare and toiletries brands, but the advertising market is expanding at more than double the IMF’s forecast of economic growth.

Internet advertising is accelerating even faster, with revenue growth of 65 per cent forecast this year and 40 per cent in 2009, as the surge in interest in gaming websites among China’s 250m online audience prompts huge growth in search engine and in-game advertising.