By 2017, U.K. e-retailers filling online orders will ship almost 2.2 billion packages, or 70% more packages than they shipped in 2012, according to a new report from U.K. e-retail association Interactive Media in Retail Group (IMRG) and Manhattan Associates Inc., which sells web-based supply chain and warehouse management software.

In 2012, U.K. e-retailers and consumers returning items bought from them collectively shipped about 1.3 billion packages, IMRG says. The company provided no immediate estimated figure for 2013.

Online shipments in the report include items that consumers return to e-retailers; the industry average return rate stands at 22%, IMRG and Manhattan Associates say.

By 2020, IMRG projects that about one-third of U.K. e-retail orders will ship to other European countries, says head of communications Andy Mulcahy. Most of the U.K. e-retailers that ship internationally now say less than 10% of their overall sales leave the country, IMRG says.

While 72% of e-retailers in the United Kingdom already ship internationally, according to a survey of 46 e-retail executives that IMRG conducted in March, the group says that international sales growth will be the main factor leading to increased shipping.

“The U.K.’s online fulfillment infrastructure was initially set up to be very U.K.-centric, focusing on getting orders into the hands of domestic customers,” Mulcahy says. “As cross-border activity increases over the coming decade, with it will come a big shift in how stock is stored, managed, controlled and monitored to serve the requirements of the global consumer audience.”

Manhattan Associates ranks No.2 among fulfillment vendors in Internet Retailer’s Leading Vendors to the Top 1000 E-Retailers.