Microsoft has cut its list of potential candidates to become its new CEO from 100 to fewer than 20, but will not make the appointment before 2014, its board announced.

This "extremely impressive" group is expected to be whittled down to one person chosen to succeed former chief Steve Ballmer early next year, said board member John Thompson in a blog post.

The revelation has extinguished hopes Microsoft had already chosen its new leader, who would be revealed before the end of the year, with ex-Nokia boss and former Microsoft employee Stephen Elop and Ford CEO Alan Mulally touted as frontrunners.

Thompson wrote: " [We] focused our energy intensely on a group of about 20 individuals, all extremely impressive in their own right. As you would expect, as this group has narrowed, we’ve done deeper research and investigation, including with the full board.

"We’re moving ahead well, and I expect we’ll complete our work in the early part of 2014. This is a complex role to fill, involving a complex business model and the ability to lead a highly technical organization and work with top technical talent."

Ballmer announced his resignation back in August, saying he would step down within 12 months once a suitable successor was found, and speculation has persisted that the board forced him out early after disappointing results in the company’s belated entry into the mobile and tablet space.

Its Surface tablet pushed the company into a $900m write down in the second quarter after terrible sales, and it has since bought Nokia’s mobile division for £4.5bn to bolster its Windows Phone OS.