The latest US mobile subscriber report reveals troubling news for Microsoft and their efforts to compete with Android and iOS. comScore surveyed over 30,000 US mobile subscribers over the age of 13 and found that users are continuing to abandon or sidestep Windows Phone devices. 

The report comes from data generated by comScore's MobiLens service which shows that Microsoft's smartphone ownership is down to just 5.8 percent for the three month average ending in June 2011. This is in contrast to their March 2011 share which sat at 7.5 percent.

Microsoft is in next to last place of the five reported smartphone platforms in the study and just ahead of Symbian which holds a June 2011 share of only 2 percent.

The successor to Microsoft's Windows Mobile platform, Windows Phone launched late last year on several carriers and devices worldwide. Microsoft was clearly late to the smartphone market but that hasn't stopped them from playing catch-up. The Redmond-based company inked a deal with Nokia in February that would see them switch to Windows Phone as their primary smartphone platform, bumping Symbian to franchise platform status.

Microsoft also recently pushed their next operating system, code-named Mango, to developers for a fall launch. The new OS will bring several updates and new features including an HTML5 version of IE9, deep Twitter integration, better multitasking support, an improved messaging system and new Bing features.

It remains to be seen if Mango will help to right the sinking ship or if its too little, too late for Microsoft in the smartphone industry.