An investor with a minority stake in Yahoo on Thursday urged Microsoft to take its most recent proposal for a partial investment directly to Yahoo shareholders and prove its merits.
Mark Nelson, a partner in Mithras Capital, which owns 1.7 million Yahoo shares, said such a move by Microsoft would help shareholders gauge whether the partial deal was truly superior to an advertising partnership Yahoo forged with archrival Google .
Microsoft abandoned a $47.5 billion offer to buy all of Yahoo last month, but more recently discussed a transaction to take a 16 percent stake in Yahoo and buy its search business for $9 billion. Talks broke down last week.
Microsoft said its alternate deal was still open for discussion, though Yahoo maintains that selling its search business would be tantamount to giving up on future growth in the wider online advertising market.
"Microsoft claims that it has a clearly superior transaction," Nelson wrote in a letter that he said was e-mailed and faxed to Microsoft Chief Executive Steve Ballmer.
"Now is the time, prior to the imminent proxy election, to substantiate that claim and take it directly to Yahoo shareholders," Nelson said.
Yahoo faces a proxy battle against billionaire investor Carl Icahn ahead of its annual shareholders meeting on Aug. 1.
Microsoft and Yahoo officials were not immediately available for comment.