UK advertisers spent £1.75bn on internet advertising in the six months to the end of June, a 4.6% year-on-year increase, according to a report by the Internet Advertising Bureau and PricewaterhouseCoopers. To put this in perspective, in 1998, when the IAB first measured internet advertising, just £19.4m was spent online.

The internet now accounts for 23.5% of all advertising money spent in the UK, while TV ad spend accounts for 21.9% of marketing budgets.

Thinkbox, the UK TV marketing body, has taken exception to the IAB's figures, arguing that the internet is now mature and diverse and it is inaccurate to collate all the figures as if it is one single medium.

"It is interesting but meaningless to sweep all the money spent on every aspect of online marketing into one big figure and celebrate it," said Lindsey Clay, marketing director at Thinkbox. "Online marketing spend is made up of many things, including email, classified ads, display ads (including online TV advertising) and, overwhelmingly, search marketing. They should be judged individually."

Despite the seemingly inexorable rise of internet ad spend, a closer examination of the IAB's figures show that the recession has had an impact. In the first quarter £920m was spent on online advertising, representing 8.6% year-on-year growth. However, in the second quarter, spend fell almost £100m to £832m, representing only a 1.1% increase on the amount spent in the same period last year.

Adam Smith, futures director at WPP's combined media operation Group M, argued that the internet's share of total UK ad spend could be close to its peak.

"This day was bound to arrive, as the internet has been attracting a huge long tail of advertisers that have not advertised before doing completely new things," he said. "It is a memorable event. However, it is a bit simplistic to make this comparison [and] it is always possible that internet's share [of total UK ad spend] could go backwards if TV has a good year."