The analyst group said online trade within the EU, which was worth £49.1bn - or 1% of total business - in 2001, would grow as firms transform sales processes and adapt to new trends such as strategic sourcing.
Forrester analyst David Metcalfe said the UK would be among the countries driving the increase in online trade.
"In 2006, Europe's three major markets - the UK, Germany and France - will transact at least 23% of sales online, and their combined trade volumes will represent a whopping 64% of the EU's total online trade," he said.
"The rapid growth and high volume of Net-based trade in France, Germany and the UK will pressure proximate countries with deep trading relationships - such as Belgium, Austria and Ireland - to accelerate their migration to the Net."
Metcalfe said online trade in industrial sectors, such as industrial machinery, vehicle manufacturing, metals, energy and utilities, will double from 2003 to 2004. "Growth in Europe's industrial sectors will account for a massive €945bn [£603bn], representing 9.9% of total business trade," he said.