It had to happen soon, and somewhere first.

At just 12% of the total advertising market in the United States, online ads still have a ways to go before surpassing the amount spent on television.

In the United Kingdom, however, the Internet Advertising Bureau (IAB) is reporting that online advertising has overtaken television. According to Reuters, advertising spend on the Internet grew 4.6% to a total of 23.5% of the total market.

On the flip side, television advertising spend plummeted 17% and dropped to second place, accounting for 21.9% of the total. That means, for the first time ever, the web is the leading medium for advertising in the UK.

IAB chief executive, Guy Phillipson says, “This is a significant milestone…This is the first major market where online has overtaken television to become the biggest single medium.” The IAB report, conducted twice a year, found that online ad spend now accounts for 1.75 billion pounds, which is roughly $2.7 billion. Reuters reports that the increase in online ad spend is a result of economic conditions that are forcing advertisers to move to the web. According to their analysis:

“The IAB report said the Internet had avoided this slump, due to the strong demand for paid-for search on sites such as Google and resilience shown by classified online ads.

Paid-for search grew 6.8 percent from the first half of 2008 to 2009, with marketers investing 1.05 billion pounds, equating to 60 percent of all online advertising expenditure.”

It’s important to note, however, that the BBC, the UK’s powerhouse network, is commercial free and publicly funded. Comparatively speaking that would be like shutting off advertising spend for a major US network like NBC, which would certainly limit television ad buys. Regardless, it’s a significant milestone in online advertising, and a trend we’re likely to continue to see as ad dollars shift to the Web around the world.

Image from horizontal.integration on Flickr