Yahoo Inc. has rejected Microsoft's latest attempt to buy its online search operations in a "take it or leave it" proposal that Yahoo said would have dismantled its internet franchise.

As described by Yahoo in a statement released late Saturday, Microsoft packaged its latest offer with activist investor Carl Icahn, a billionaire seeking to overthrow Yahoo's board of directors in a shareholder meeting scheduled for Aug. 1.

Without providing many specifics, Yahoo said Microsoft renewed an earlier bid to buy the company's search engine and proposed turning over the remaining pieces to a board controlled by Icahn.

Yahoo said it received the complex proposal Friday and was given less than 24 hours to respond.

Backed into a corner, Yahoo lashed out in a blunt manner likely to inject even more bad blood into its already venomous relationship with Microsoft and Icahn.

"Carl Icahn and Microsoft presented us with a take it or leave it proposal,'' Yahoo chair Roy Bostock said in a statement. "It is ludicrous to think that our board could accept such a proposal.

"While this type of erratic and unpredictable behaviour is consistent with what we have come to expect from Microsoft, we will not be bludgeoned into a transaction that is not in the best interests of our stockholders."

Microsoft did not immediately respond to a request for comment late Saturday. Efforts to reach Icahn were unsuccessful.

Yahoo said it unsuccessfully reiterated its willingness to sell the entire company to Microsoft for $47.5 billion, or $33 per share — a bid that the software maker dangled in early May before withdrawing it in a pique over Yahoo chief executive Jerry Yang's demand for $37 per share.

Opportunity to sell Yahoo fell through in May

The breakdown of those takeover negotiations infuriated many Yahoo shareholders who fear the company's stock price would plunge back below $20 — a threshold reached just before Microsoft made its initial bid in early January. Yahoo shares finished Friday at $23.57.

Yahoo's squandered opportunity to sell to Microsoft in May prompted Icahn to lead a rebellion aimed at removing Yahoo's entire board so he could fire Yang and try to revive sales talks with Microsoft.

Icahn's attempted coup gathered more steam earlier this week when Microsoft publicly announced it might be willing to buy all or part of Yahoo if shareholders voted to remove the current board. Yahoo shares climbed 10 per cent during the past week on hopes that Microsoft's backing of Icahn might pave the way for a deal.

Since it dropped its bid to buy all of Yahoo, Microsoft had focused its overtures on Yahoo's search engine — the second most used on the internet behind Google Inc.'s.

Microsoft in May offered to buy Yahoo's search operations for $1 billion, and to spend another $8 billion to acquire a 16 per cent stake in Yahoo's remaining operations.

Yahoo said the proposal that Microsoft submitted Friday "contains a number of improvements," but insisted it still wasn't good enough.

Yahoo offered no concrete details about what Icahn had proposed to do with the rest of the business, but indicated part of the plan included selling the company's Asian operations. The Sunnyvale, Calif.-based company pooh-poohed the notion of entrusting its business to Icahn, noting his inexperience in the internet industry.

Icahn, who has been challenging corporate boards for more than two decades, owns a roughly five per cent stake in Yahoo and hopes to make a profit by pushing the company's stock price above $30.

Instead of selling its search engine to Microsoft, Yahoo opted to forge an advertising partnership with rival Google Inc. That represented a bit of irony because Google's dominance of the internet search advertising market is the primary reason Microsoft is pursuing Yahoo.

As Google has become more successful, both Yahoo and Microsoft have been regressing, a dynamic that many analysts believe make it imperative for the two companies to put aside their differences and combine forces.

Yahoo has estimated it can boost its annual revenue by about $800 million by relying on Google's superior technology to show some ads alongside the search results on its website.

But Yahoo's alliance with Google is being closely vetted by antitrust regulators because the two companies together control more than 80 per cent of the U.S. search advertising market.

To accommodate the review, Yahoo and Google have voluntarily agreed to wait until late September to begin working together.