The IAB claims the UK online advertising industry will lose £187m if the European Parliament approves amendments to the 1997 ISDN directive that will classify cookies as spy devices.
The EC claims cookies threaten privacy because they collect information on people's web browsing without consent.
The bureau said cookies help consumers get the best out of the internet, and to tamper with this will have a negative impact on both users and internet business.
"If cookies are made illegal, forcing customers to give explicit consent, it will be bad for websites that make money from advertising and it will be more difficult for consumers to use the web efficiently," said Robin Jezek, secretariat at the IAB.
Major industry figures are behind the IAB campaign, and companies such as Yahoo! and MSN have declared support.
"Cookies serve a number of functions to help consumers make better use of the internet. They allow consumers to receive useful, personalised content, and can save on time and inconvenience," said Martina King, managing director at Yahoo! UK.
Others believe cookies play an important role in ensuring the internet offers alternative advertising, and warn that the sector could suffer if advertisers are deterred by new rulings.
Gareth Bullock, media director at Tribal DDB in London, said: "To maintain consumer choice, to maintain an alternative advertising channel to the American-dominated media owners, and to ensure that advertising can remain relevant to the consumer, cookies are essential.
"If cookies go, commercially-driven European media owners will withdraw from the sector. Regulators need to understand the value and benefits to the individual, advertisers and to European media owners before committing hara-kiri."
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