Nearly half of in-store retail sales in Europe will have been influenced by the internet within the next four years.
This is according to new research from Forrester, which forecasts that in 2018 44 per cent of purchases in a shop will have been researched online first.
Such a figure is the equivalent of €920 billion (£752 billion), representing significant growth on the €539 billion recorded last year.
The UK will play a major part in this growth, with Forrester expecting the country to account for 72 per cent of these cross-channel sales along with France and Germany. It said these findings show how important it is for businesses to have an online presence even if they do not actually make sales over the web.
Michelle Beeson, an analyst at Forrester, said the growing popularity of mobile devices is having a big impact on the internet's influence on retail.
"The near-ubiquitous connectivity of mobile devices, and smartphones in particular, gives shoppers a personalized and connected shopping aid in multiple contexts along the path to purchase," she stated.
"Online retailers need to optimize their customer journey to take advantage of the 'mobile moments' in which a customer needs service or information and uses his mobile device to obtain them," Ms Beeson added.
Forrester said people are increasingly using Amazon as a means of researching products online and often check an item here rather than on the website of the store they will actually buy it in. It found 25 per cent of adult European internet users look at an item on the web before purchasing.
The organisation said the five categories in which people will cross-channel shop most often over the next four years will be household appliances, toys, electronics, computers and sports equipment. In each of these areas cross-channel sales are expected to account for between 54 per cent and 73 per cent of total sales.