In its latest mobile browsing and booking trends report, brand consultancy Nucleus also found that mobile had rised to 43% of all website traffic in June 2014.

Apple remains the dominant operating system, with 77.9% share and 87.8% of bookings, while Android accounts for just 19.6% of the market.

Brands that have invested in responsive design or smartphone-friendly websites are naturally seeing better mobile results, with luxury sites reportedly leading the way.

However, despite evidence that users are increasingly shifting to mobile, and Google’s warnings about penalising mobile-unfriendly sites, the travel sector was found to be lagging when it comes to implementing responsive web design.

Founder and chief executive of Nucleus, Peter Matthews, said: “We are in our fourth year of studying the growth in mobile web browsing and are seeing further significant shifts in user behaviour with affluent smartphone users, in particular, now completing high value bookings on their phones.

“Wider availability of 4G and the launch in September of the larger screen iPhone 6 are likely to accelerate this trend.

“It’s surprising in this context that there are still so many travel brands without either a mobile-friendly website or app and fewer still taking advantage of the flexibility and efficiencies of responsive design. This prolonged inactivity is beginning to look like a death wish.”