Another Christmas without a universal 4G service will cost the UK economy £120 million in lost sales, according to a study.
Slow connection speeds are set to pose a barrier for many consumers wanting to shop via their mobile phones, and a nationwide roll-out of 4G would have boosted sales from £373 million to £493 million, the report by online auction site eBay claims.
More than half of consumers (55%) plan to use their mobile to browse the web this Christmas, while 39% say they will use their device to get gift ideas and check prices.
And eBay.co.uk said it expected to see around a third of items in its Christmas campaign bought through a smartphone.
It said the top three barriers preventing consumers from shopping on their mobiles were slow connection speeds, payments timing out and network reliability - all problems effectively eliminated by 4G.
EE, formerly known as Everything Everywhere, has started to launch its range of 4G products and services in London, Bristol, Birmingham, Cardiff, Leeds, Sheffield, Edinburgh, Glasgow, Liverpool, Southampton and Manchester.
The network, which offers speeds up to five times faster than 3G, will be available on the Apple iPhone 5 as well as devices from HTC, Samsung, Nokia and Huawei.
Clare Gilmartin, vice president of eBay Marketplaces Europe, said: "Mobile devices have become virtual stores in our pockets, giving us the ability to shop anytime, anywhere. But for consumers, it's critical that the experience is quick, seamless and simple. Slow browsing speeds and breaking connections are now significant barriers to mobile commerce - and this comes at a high price.
"While we welcomed the move by Ofcom to bring the 4G spectrum auction forward to early 2013 there's no doubt, as this research shows, that for the UK economy the cost of another Christmas without universal 4G is huge.
"Consumers are increasingly demanding a better experience, regardless of their network. We hope that the Government will work quickly come the New Year to ensure its promise to deliver 4G for all by the end of 2013 is realised."