Last week's increased buyout offer for Dell (NASDAQ: DELL) coming from Michael Dell and investment firm Silver Lake, with that offer's accompanying request for a change in proxy voting rules, has elicited a response from buyout opposition leaders Carl Icahn and Southeastern Asset Management.

Today, Icahn and Southeastern issued an open letter to the special committee of Dell's board of directors, saying that the change in "the voting method for 'Unaffiliated Stockholder Approval' for the proposed Michael Dell/Silver Lake freeze-out merger raises serious questions for the Special Committee."

The original agreed-upon rules call for non-voted shares to be cast as "no" votes to the buyout. Michael Dell wrote the special committee last week that the rule should be changed because it allows a minority of unaffiliated stockholders to then block the deal. Shares that aren't voted should be ignored, he said, to allow the majority of unaffiliated stockholders to decide the vote.

But as Icahn and Southeastern wrote: "Michael Dell and Silver Lake agreed to a specific voting requirement to approve their deal. ... [They] have now offered to pay a dime for a new method of voting designed to prevent stockholders from passively dissenting on the proposed merger. We view this as a cynical attempt to circumvent the process."

Last Wednesday, Michael Dell and Silver Lake increased their offer from $13.65 a share to $13.75 a share. At that time, Dell's special committee adjourned the stockholders meeting without the scheduled buyout vote and rescheduled it for Aug. 2.

Fool contributor Dan Radovsky and The Motley Fool have no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.