LONDON: UK advertisers spent a record £3.98bn on digital advertising in the first half of 2015, according to a new report, driven by a surge in mobile advertising revenues.

Figures from the Internet Advertising Bureau UK Digital Adspend report, conducted by consulting firm PwC, show that total digital ad spend was up 13.4% in the first six months of the year with mobile accounting for most of this.

Ad spend on mobiles increased 51% to £1.08bn over the period; the actual increase of £370m year-on-year accounted for 79% of the rise in digital ad revenues.

Over a quarter (27%) of all digital advertising spend now comes from mobile, compared to 20% a year ago. Mobile accounts for 39% of display spend, 43% of video spend, 63% of social media spend and 74% of native/content ad spend.

"Mobile is unquestionably the engine of digital growth," said Dan Bunyan, Senior Manager at PwC. "However, there's plenty of room to grow, as mobile accounts for 40% of internet time but only 27% of ad spend. Marketers are realising this is out-of-kilter, hence mobile is likely to continue gaining share at pace."

Despite concerns about the possible impact of ad blocking, the IAB reported that display advertising revenues had grown at more than twice the overall digital rate (27.5%) to hit £1.31bn. This represented 33% of total digital ad spend, its largest-ever share.

Within that, video ad spend was up 56% to £292m, accounting for 22% of display revenue, while native/content grew 50% to £325m, taking a 25% share.

Paid-for search marketing still takes over half of all digital ad spend, increasing 8.4% to £2.07bn in the first half, while classifieds, including recruitment, property and automotive listings, grew 6.6% to £547m, accounting for 14% of digital ad spend.

"It's clear to see the UK digital advertising industry is maintaining its strong revenue growth at a much greater rate than the overall economy," said Tim Elkington, Chief Strategy Officer, IAB UK.

"The fact remains, as consumers spend more time on connected devices, advertisers must increasingly direct their attention and budgets there," he stated.

The latest figures from Warc's Adspend Database, which tracks advertising expenditure in 90 markets across eight major media, show that the UK leads all other European markets in terms of mobile adspend, while it also ranks third globally, behind only the US and China.

Data sourced from IAB UK; additional content by Warc staff