He pointed out that the letter was more than a month old and that Rinehart apparently appeared frustrated at the obfuscation by Corbett in not fully disclosing what she was agitating over.
Last month, Fairfax appointed her close ally, Hungry Jack's entrepreneur Jack Cowin, as an independent director in what was viewed by some as a friendly olive branch.
"I think this [letter] is a bit of a warning sign. She's saying back to the board and Roger Corbett, 'You can put Jack Cowin on the board, he may be a business associate and mate but I'm still after two board seats and I'myour number one shareholder,"' Allen said.
"I think it's very clear that she's saying, 'I'm not going anywhere, I'm not giving up and I'm the only one buying shares."'
The letter states that shareholder value has been declining for five years under Corbett.
The chairman owned 0.004 per cent of Fairfax's issued capital and collectively all the directors owned 0.15 per cent, which was "exceedingly little skin in the game", it said.
Klepec also criticised the Fairfax board for not arranging directors' and officers' insurance, which had been used as a reason to block Rinehart from becoming a director.
"We believe Fairfax Media is a company whose performance can be improved with the right direction and resources and your support," the letter said.
Rinehart began pressing for board seats after her mining company, Hancock Prospecting, became the media group's biggest shareholder this year. Its current stake is 14.9 per cent.
- AAP