Christmas sales influenced or purchased via smartphones will hit £3.5bn, says research from advisory firm Deloitte.

But £330m of sales will be made directly through the devices, as Deloitte says the influence of smartphones “far outweighs” the value of direct sales made through them. Shoppers have been using them more and more while in-store to research prices, store Christmas shopping lists, use social networking sites and make payments.

10% of all in-store retail sales will be influenced by smartphones this festive season, Deloitte predicts. This figure will rise to 18% for the full year in 2016, equivalent to £43bn of sales.

This Christmas, online sales are expected to jump 1% to 17% of total sales, while £500m of sales will be made through tablets.

The use of click and collect is expected to rise too.

Deloitte head of multichannel retail Colin Jeffrey said: “Retailers without flexible collection options and mobile services are failing to meet basic customer expectations and will suffer as a result.”

Deloitte UK head of retail Ian Geddes said he remains cautious over the long-term outlook for UK retail but, with an improvement in consumer confidence and a drop in inflation this Christmas against last, it is expected to generate “modest growth”.

He added: “However, while we forecast the value of retail sales to be in positive territory, once you account for inflation running at 2.5%, this equates to a fall in volume. Yet, with retailers increasing their focus on stock control we would expect to see better use of strategic, targeted sale activity as opposed to the blanket application of discounts across stores seen in recent years.”

Geddes predicts general merchandise sales to be flat or fall slightly as, with rising food prices, shoppers save for Christmas dinner.

But he said underlying this is the attractiveness of the retailer’s offer.

He said: “Increasingly, we are seeing examples of certain retailers performing strongly and others weakly within the same sector. Shoppers are responding to those retailers that combine the right products with exceptional customer service across all channels, dynamic and exciting online and mobile sites and a brand that they want to be associated with and invest in.”