Microsoft has blamed smartphone makers for the delay in the roll-out of software updates to smartphones running Windows Phone 7.

The first major upgrade to the mobile operating system will bring a copy and paste function to the handsets, along with shorter start up times for applications and games, and better search features on Microsoft's application store Marketplace, which should now also be more stable when downloading apps, according to Microsoft. The company has made smaller improvements to Facebook integration, Wi-Fi connectivity, Outlook and camera stability.

However, despite being announced in March, the roll-out of the update has been a lot slower than smartphone owners hoped. Microsoft also ran into problems earlier this year when a smaller update caused Samsung smartphones running the OS to crash. Users are furious with the delays and even resorted to bombarding a Microsoft blog with angry comments.

"We had expected it to be earlier than now," Joe Belfiore, head of Microsoft's Windows phone program, said at a software developer conference in Las Vegas, according to Reuters.

Belifore said they had discovered some handsets would not function properly after installing the update, although he declined to name the manufacturers behind the problematic phones. Samsung, HTC and LG are the three biggest makers of handsets running the OS.

"We felt it would be better to be a little bit patient, make sure that when we get updates out that they would happen reliably, and unfortunately that caused a delay in getting things out," he said.

However, Belifore said Microsoft has since overhauled the update and is "optimistic" there will be no further problems with future updates.

Earlier this month, Microsoft advised Windows Phone 7 users not to deploy an unauthorised tool to update the software on their handsets. Developer Chris Walsh released the tool that let WP7 users download the two updates that Microsoft has struggled to push out.

However, when Microsoft got wind of the tool, it urged handset owners not to use it.

"If you attempt one of these workarounds, we can't say for sure what might happen to your phone because we haven't fully tested these homebrew techniques," Eric Hautala, general manager of customer experience engineering for Windows Phone, wrote in a blog. Users might not end up getting device-specific software that is in the official update or their phones may get misconfigured so as to not receive future updates, he said.

Walsh appears to have pulled the updater since Microsoft's warning.