Microsoft has poured cold water on hopes the departure of Yahoo chief Jerry Yang could lead to a renewed offer for the company.

The software giant's chief executive, Steve Ballmer, said he was no longer interested in the company as a whole but could restart talks on an internet search partnership.

"Let me be as clear as I think I've tried to be publicly. We are done with all acquisition discussions with Yahoo," Ballmer told Microsoft's annual shareholders meeting. "We thought we had something that made sense. It didn't make sense to them. We've moved on."

Ballmer's firm had been offering $31 a share in a deal worth $47.5 billion (£31.55 billion) until driven away by Yang earlier this year.

Yahoo shares fell 19% to close at $9.14, their lowest in six years, after Ballmer's comments.

After Yang rejected Ballmer's bid as too low, Microsoft offered to buy Yahoo's search business, but Yahoo decided instead to sign a search advertising deal with Google. That deal has fallen apart after opposition from competition authorities.

Ballmer also signalled some problems of his own, and said Microsoft is looking for areas to cut costs with the prospect of slower growth this year and next.

Some analysts say Yahoo has fallen so far that investors have overlooked the company's cash pile of $3.3 billion - some $2.38 a share - which makes it richer per share than Google.

Brokerage Collins Stewart estimates Yahoo has an additional $2.90 per share, or $3.3 billion, in off-balance sheet assets, mainly through stakes in a host of Asian internet companies.