The cross-media campaign, covering TV, press, outdoor, ambient and online advertising, challenged SMEs to call O2 to find out the best mobile solution for them in two minutes.
The judges of the annual awards said the two-minute challenge campaign "took a completely fresh approach to targeting the SME sector and ripped up the rulebook for advertising mobile services to businesses".
The runners-up for the Advertiser of the Year award were Vodafone, Esure Insurance, Yorkshire Water Services and Walkers Snack Foods.
Fresh drinks company Innocent also picked up a gong for its marketing strategy at the awards, known as the "business Oscars". The judges said smoothie manufacturer Innocent was "an incredibly forward-thinking company using an innovative range of marketing to drive brand recognition".
Innocent relies heavily on PR and in the past year more than 1.3m samples of the drinks have been tasted. The company has also launched three new product lines, seasonal drinks, and a flavoured water range in response to customer feedback.
Duncan Painter, CEO of marketing award sponsor ClarityBlue, said: "More than any other organisation, Innocent Drinks has demonstrated what a strict focus on detail, quality of brand presentation and, above all, innovation in the distribution of its message with accountability has ensured a true return on investment for its business."
The runners-up for the Marketing Strategy of the Year were Loyalty Management UK, Nationwide Building Society, the Royal Bank of Scotland Commercial Services, and West Bromwich Building Society.
There were more than 1,900 nominations for the National Business Awards 2003, created by publishing and events company Quest Media to recognise commercial success, innovation and ethics among UK businesses of all sizes.
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