Irritated by ads within smartphone apps? Prepare to be annoyed even more in the future. Annual global advertising spend on mobile devices is expected to reach $105 billion (€94 billion) by 2019, more than double the estimated size of the market – some $51 billion – this year.

Juniper Research, which produced the figures, said the rise of mobile advertising is partly the result of "an attitude shift" among brands and retailers, many of which are now using mobile as "a core channel for consumer engagement", in part because of smartphones' ability to deliver targeted, personalised and timely advertising.

Mobile devices will account for 44 per cent of total digital ad spend by 2019, it forecasts, while spending on smartwatch advertising – estimated at $1.5 million this year – will rocket to $69 million.

This shift in ad dollars has come alongside a surge in advertisers’ enthusiasm for exploiting Big Data analytics that help them gain insights into consumer purchasing patterns, both online and offline.

But Juniper’s media analysts warn that brands may suffer negative publicity, as well as possible legal action, if they don’t seek consumers’ opt-in consent before sharing data.