Spending on Internet advertising in the UK has surpassed expenditure on television advertising for the first time, according to a study by the Internet Advertising Bureau and accountant PricewaterhouseCoopers.Online spending rose by 4.6% year on year to £1.75bn in the first half of 2009, while spending on TV ads declined by 16.1% to £1.64bn.Overall advertising in the first half of 2009 was down 16% year on year.Thinkbox, the marketing body for commercial TV in the UK, cried 'foul' after the report was published, however, saying the figures did not compare like to like.Thinkbox, which counts Channel 4, Five, GMTV, ITV, Sky Media, Turner Media Innovations and Viacom Brand Solutions among its shareholders, complained that the many strands of online spending - e-mail campaigns, classified ads, display ads and search engine keyword ads - should be measured individually.'The internet is a fantastic technology and home to many different marketing activities that do different things. As such, it is interesting but meaningless to sweep all the money spent on every aspect of online marketing into one big figure and celebrate it,' claimed Lindsey Clay, Thinkbox's marketing director.Despite Clay's protestations, the rise in popularity of advertising online presents a major threat to commercial television broadcasters, particularly those not protected by a 'pay per view' or subscription based element in their revenues. The Internet Advertising Bureau (IAB) observed that in 1998, when it first started measuring Internet advertising spend, the amount spent online by advertisers was just £19.4m. The IAB had predicted that online spending would overtake TV expenditure by the end of 2009 but the milestone was achieved six months earlier thanks to the collapse in TV advertising, brought on by the economic downturn.Guy Phillipson, the chief executive of the IAB, predicted that annual spending on Internet advertising could 'go past £4bn to even £5bn annually.' The UK is the first major economy where online advertising spend has overtaken TV advertising expenditure, although the milestone was achieved in Denmark around six months ago.