Google continued to increase its US search market share last month, according figures from comScore.

The search engine’s share of the market rose from 58.5% to 59.2% in February; while rivals Microsoft and Yahoo saw their figures drop slightly.

Yahoo’s share slipped to 21.6 percent, from 22.2 percent a month earlier, while Microsoft’s share slipped to 9.6 percent from 9.8 percent.

AOL is clinging to a 4.9 percent share, while Ask saw its share rise slightly to 4.6 percent from 4.5 percent in January.

UK figures for February are unavailable, but Hitwise stats from January give the search engine a massive 90% market share in this country.

Meanwhile, comScore also reported that clicks on Google’s paid search ads declined between January and February, the first time that this has happened three months in a row.

Google’s paid click rate did grow, by 3.1% in February, compared to the same month last year, but this is modest compared to the 40% growth rate of just over six months ago.

The search engine did outperform it rivals though, with the average paid click growth rate of 0.9%. The figures have concerned the markets though, with the value of shares falling after the news.

Some changes made by Google may have been responsible for these paid search numbers. Google said recently that it has been removing ads that generate low click through rates or that direct users to low quality Web sites.