Google has defended recent changes to its search system that reduced the prominence of some popular websites.
One of the worst hit by the "Panda" update was Ciao.co.uk, a Microsoft-owned company that had been leading an EU competition case against Google. Its web visibility fell by 94% according to analysis by Searchmetrics.
Google's head of search evaluation, Scott Huffman, said it was "almost absurd" to suggest that the results were rigged.
However, experts said that it was unusual to see a legitimate website hit as badly as Ciao. "A 94% drop is astronomical," said Sanjay Shelat, a search engine optimisation (SEO) specialist at Edit Optimisation.