Google's share of the UK search market has dropped to below 90 per cent, according to a company that monitors web traffic.
The 89.33 per cent share is Google's lowest in five years, says Experian Hitwise.
Microsoft's Bing is in second place, with 5 per cent of UK searchers opting for it. Yahoo's Ask - previously known as Ask Jeeves - is in third.
Experian Hitwise used data from ISPs to analyse the searches of 8 million people in the UK.
Experts say Bing's extensive marketing has made it more popular as well.
Luca Paderni, an analyst from Forrester Research, told the BBC: "In the UK, Bing has been using very aggressive tactics of promotion for the last few months in preparation for the Christmas season.
"But Google is still dominant, and we would need to see a trend over more months to call it a consistent decline."
Competition around the globe
Google may still have a huge lead in the UK, but in some territories it's playing second fiddle to home-grown alternatives.
In China, most searchers opt for Baidu, while in Russia, Yandex outs Google to the top spot.
In order to stand a chance against Google, search engines will have to become more specific, according to Paderni.
"There's increasingly more space for search services specialising in specific industries or topics," he said.
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