The number of tablet PCs running Google Android has surged, but Apple remains the market leader, says Strategy Analytics.

According to the market research and consulting firm, 26.8 million tablets were shipped in Q4 of 2011, which is a 150 percent increase on the 10.7 million shipped in the same quarter of 2010. Nearly two in five (39 percent) of the tablet PCs shipped during the end of 2011 ran Google's open source operating system, up from 29 percent the previous year.

However, 57.6 percent run Apple's iOS software, indicating Apple's iPad has retained its crown in the tablet PC market.

"Demand for tablets among consumer, business and education users remains strong. Apple shipped a robust 15.4 million iPads worldwide and maintained its strong market leadership. Apple shrugged off the much-hyped threat from entry-level Android models this quarter," said Peter King, Director at Strategy Analytics.

Strategy Analytics also revealed global tablet PC shipments hit 66.9 million for the whole of 2011, which is 260 percent up on the 18.6 million shipped in 2010.

"Android is so far proving relatively popular with tablet manufacturers despite nagging concerns about fragmentation of Android's operating system, user-interface and app store ecosystem," added Neil Mawston, executive director at Strategy Analytics.

The research firm also revealed that Microsoft had managed to capture just one percent of the tablet PC market.

"The upcoming release of Windows 8 this year cannot come quickly enough for Microsoft, so its hardware partners can start competing more effectively in the tablet space," the firm added.