NEW YORK: The Interactive Advertising Bureau has asked leading online research firms comScore and Nielsen/NetRatings to submit to an audit amid concerns they have reported different audience sizes for the same websites.

As advertisers shift dollars into online digital media, precise measurement of how and where users spend time on the web is increasingly important.

Avers IAB ceo Randall Rothenberg: "We simply cannot let the internet, the most accountable medium ever invented, fall into the same bad customs that have hindered older media and angered advertisers for decades."

He adds in a statement: "The goal of the IAB and the entire interactive industry is simple: to achieve transparency in audience counts and to revise out-of-date methodologies."

ComScore has reportedly agreed to the IAB's request, while Nielsen is still considering its response.

Data sourced from Wall Street Journal Online; additional content by WARC staff