The Guardian reports that Internet ad spend in the UK, at £1.75 B in the first 6 months of the year, overtook TV ad spend for the same time period. This was aided by the advertising recession. Internet ad spending now represents a whopping 23.5% of all ad spending in the UK, compared to 21.9% for TV. Spending on online video, while having grown 300%, still represents just a tiny £12 M sliver.
It's not surprising that the UK is the first major economy where this is the case given that the BBC's distorting impact on the media landscape. It has a lot of viewership (and listenership and readership) but is of course non-commercial and so there the ad £ will naturally look for other outlets. It is also a valid point that the internet actually comprises several mediums including search, display, email, online video and other formats, and so comparing 'internet' to TV is not a fair comparison. Nevertheless, it is a milestone worth noting.