Biggest is not always best when it comes to keyword placement advertising on search engines, research has claimed.

Google had the highest number of searchers in December last year, according to the research by Nielsen//NetRatings, and had the highest click-through rate of any search engine in the UK.

But the researchers warned that other search engines could get ignored, despite their success at generating click-throughs.

For example Tiscali, ranked number 12 in terms of audience, generated 7.8 click throughs, making it the fourth most successful search engine in terms of click-throughs.

Similarly AltaVista Search was ranked at 15 in terms of audience, but came third in terms of number of click-throughs per searcher.

This information is crucial when assessing how to allocate budgets, according to Nielsen//NetRatings.

The research firm's head of data analytics Tim Roe said: "The research shows that, when it comes to placing keywords on search engines, a bigger audience is not always better.

"Understanding that the smaller search engines can be as successful as some of the larger ones in generating click-throughs can help companies to improve their return on investment, and make their promotional spend go further.

"There are many factors that influence the success of a search engine. As with other forms of advertising, companies cannot rely solely on the size of the audience to a particular search engine as a guarantee of attracting the right target audience to their website, product or service."