He's the man putting pressure on Motorola to sell its ailing phone business, and now Carl Icahn has turned its unwanted attention on Yahoo.

It may have fought off the advances of Microsoft, but now the billionaire activist investor is leading a mutiny after increasing numbers of shareholders voiced their anger over how the $44.6bn bid was handled.

Rumour has it that shareholders actually contacted Icahn to urge him to get involved.

The billionaire has since bought 50 million shares in Yahoo and is now to head up a proxy battle to oust the current Yahoo board, led by the company's co-founder and chief executive Jerry Yang.

Icahn says that he has already found a slate of 12 alternate directors, which he fight to replace the present board when it gets together for its shareholder meeting on 3 July.

The deadline for nominating a new board is today (15 May).

Those in the know say that Icahn will push for Yahoo to restart talks with Microsoft - and he has the support of some shareholders.

One, in fact, is launching his own battle to force Yahoo back into talks.

Disgruntled investor Eric Jackson claims: "Yahoo's stock has essentially been flat for the last four years while the market has gone up over 30% and Google has gone up 440%. So the comparisons are stark and the board has not been doing its job".

He is launching his own bid to get shareholders to "vote no" to re-electing the present board.

"I want to send a message to all board directors that they are accountable and need to be replaced", he said.

Yahoo is not commenting and neither is Microsoft.