Fasthosts has been banned from claiming it is the "UK's Number one web host" in adverts, after a rival complained it was used flawed data and exaggerated graphs to mislead potential customers.
The Advertising Standards Authority (ASA) upheld three complaints against the Gloucester-based firm last week, because it found its claims were untrue and unsubstantiated.
The complaint came from rival GX Networks, formerly known as Pipex web hosting. Fasthosts had used out-of-date data from the research firm Netcraft to support its assertions in print and online that it had "over two times more UK hosted websites than its nearest competitor", the ASA found.
The watchdog also said it was concerned that there was no agreement that having the most domains or hostnames implied market leadership.
GX Networks also complained that Netcraft had collected inaccurate data last year when it was ditching its Pipex branding.
"Because the ads used data for the period in question that had been shown to be flawed and because the ads did not make sufficiently clear the basis of the claims, we concluded that the ads were likely to mislead," the ASA wrote.
Fasthosts was ordered not to repeat its leadership claims in future, unless it had comprehensive and contemporary data to show that by value or volume, it was the top selling web host. ®