CEO John Burbank said the expansion represents “an extraordinary leap in the measurement of web audiences”, increasing the number of websites reported on by the company from 3,000 to 25,000.

The firm said the bigger panel will give the ratings data “greater depth and breadth”, while integrating respondents from the combined TV/internet measurement panel will lead to increased coverage of cell-phone only households, Hispanic households and information from secondary computers in homes.

Burbank said: “The blend of the industry’s only probability sample with a larger online sample will help deliver greater stability of audience metrics, particularly for smaller sites and the work universe. This means that clients will benefit greatly from the increased work sample and stability of the metrics reported for work audiences.”

He said the expanded NetView panel would be the largest of its kind in the US market and would benefit clients by providing deeper analysis of many sites, including “greater demographic granularity” and reach/frequency analysis for websites that had previously had too small a sample to be fully reported.

Nielsen’s online ratings have come under fire recently, with web TV firm Hulu and the New York Times claiming their sites had been undercounted. Meanwhile, earlier this month, rival ComScore detailed its new Media Metrix 360 web measurement tool, which combines information from panel members with data from ad and website servers.