The move roughly doubles the amount of exhibition space and visitor numbers normally enjoyed by each event.
IDMF owner Reed Exhibitions and Internet World owner Penton Europe said the joint shows would cater for vendors right across the interactive marketing spectrum.
Darren Whitehead, exhibition director of the IDMF, said the decision was taken in the light of research showing pressure on marketers to make their work more accountable and measurable, as well as the increasing integration of traditional direct marketing with email, SMS and the internet.
"The direct marketing discipline, with its understanding of customer acquisition and retention -- together with measurability -- is increasingly inseperable from the digital marketing channel," he said.
Internet World 2005 is currently on its last day at Earls Court 2, having opened on June 14.
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