Shoppers are also being tempted by links and adverts on social media platforms like Facebook and Instagram.
One in every five pounds spent in shops now comes via online payments, with the figure rising every year.
Shoppers told USwitch they liked shopping on a smartphone because they could do so at any time, while easily comparing prices and seeing a superior level of choice. Shopping also said they felt they could get the best value online.
Clothes are by far the most popular product bought online (69 per cent) ahead of books (51 per cent), groceries (47 per cent) and theatre or cinema tickets (43 per cent).
Ru Bhikha, mobiles expert at uSwitch.com, says: “For so many of us now, our smartphone is an extension of our hand and we have it with us at all times, meaning that we can shop whenever and wherever we like. Our handsets allow us to window shop all the time, and if we see something we like, it is right there at our fingertips.
“With smartphone and tablet shopping now a £25 billion industry, it’s hardly surprising that major retailers have long adopted a mobile-first approach to their websites and have even introduced their own apps to make the user experience as easy as possible.
“Cleaner user journeys and the ease of one-click purchasing will only add to the number of people shopping on their phones and tablets.”