Microsoft pulled the plug on Windows Phone 8.1 software, marking the end of its backing for one of the biggest ever updates to its troubled mobile operating systems.

Ending support for Windows 8.1 comes three years after the update was first introduced. The software introduced the company’s Cortana digital assistant, a changed UI, updates to its core mobile operating system, and a new notification calendar.

It was the fourth iteration of Microsoft’s mobile software, all versions of which struggled to compete in the smartphone market with the iPhone and Android offerings

The move means there will no longer be updates for a vast majority of Windows Phone powered smartphones.

Nearly all Windows phones are still running on Windows Phone 7, Windows phone 8 or Windows 8.1, but all of these are now officially unsupported, The Verge reported. Some 20 per cent of all Windows Phone devices, meanwhile, run on the latest Windows 10 Mobile OS.

Microsoft said it will continue its backing of Windows 10 Mobile for a long time.

Despite its struggles, Microsoft is yet to officially kill off its phone OS efforts, but the company clearly edged away from focussing its efforts on Windows for phones.

The company effectively exited the feature phone market in 2016 after offloading a business it acquired with its Nokia devices buy.

It also cut 1,850 jobs as part of a move to “streamline” its smartphone hardware business.