LONDON: Mobile video advertising is the fastest growing digital ad format in the UK, almost tripling in the year to June according to latest figures.

The Internet Advertising Bureau UK Digital Adspend report, conducted by PwC, showed total digital ad expenditure had risen 16.6% year on year to a record £3.5bn. And while mobile video ads formed only a small part of the total, at £63.9m, that figure represented a 196% increase on the same period a year earlier.

Overall mobile ad spend rose 68% to £707m and it now accounts for 20% of all digital advertising.

"Mobile's share of the digital ad pie has tripled in two years, accounting for a fifth of total spend – rising to nearly a third of display and over half of social media ads," said Dan Bunyan, manager at PwC.

"As 4G becomes more prevalent and phone screens become larger, it will play an even bigger role in driving digital ad spend – particularly video," he added.

Data from YouGov which accompanied the report highlighted the drivers behind the growth in video advertising. Almost three quarters of online Britons who own an internet-enabled device had watched TV programmes online during the last six months. Further, 72% had watched short online video clips and 59% had watched films online.

"Average weekly viewing online amounts to 25 videos, 4-5 TV episodes and one film," said Tim Elkington, chief strategy officer at IAB UK.

"But what's most interesting is that watching video on connected devices is becoming an increasingly social activity, like traditional TV," he added. "Half of people watching TV, films or video clips online do so with family members and three in ten watch with friends."

In terms of the different advertising formats, display advertising across the internet and mobile grew almost twice the overall digital rate at 30.1% to reach £1.02bn in the first half of 2014, the report said. Paid-for search marketing grew around a third as fast, at 11.3% to £1.92bn, while classifieds, including recruitment, property and automotive listings, grew 14.4% to £493.5m.

Consumer goods' advertisers spent the most on digital display advertising, accounting for 16% of the total in the first half of 2014, followed by travel & transport (15%) and finance advertisers (13%).

The consumer goods category was also the biggest spender on mobile display ads, taking a 23% share followed by entertainment & media (21%) and technology (12%).

Data sourced from IAB UK; additional content by Warc staff