Billionaire investor Carl Icahn has resigned from his position on the board of Yahoo!, saying the US Internet giant no longer needed an "activist" director like him.

"I don't believe that it is necessary at this time to have an activist on the board of Yahoo! and currently, my attention is focused on other matters," Icahn, one of the company's largest shareholders, wrote in a resignation letter to the board, a copy of which was provided by his office.

"As a result, I do not presently have the time that is necessary to devote to the business and affairs of Yahoo! required if a board member is to fulfil his fiduciary duties to the shareholders," he added.

A spokeswoman for the investor, Susan Gordon, said in a statement that Icahn "indicated that there are a number of other companies on which he is currently focused." Icahn -- a financier who has developed a reputation as a corporate raider -- on Monday offered a six-billion-dollar loan to ailing lending giant CIT Group.

In late August Icahn sold 12.7 million shares in Yahoo!, cutting his stake in the company a month after it formed an Internet search partnership with software giant Microsoft.

Last November, following the decision of Yahoo! co-founder Jerry Yang to step down as head of the Internet firm, Icahn increased his stake in Yahoo! to 5.4 per cent, up from the 5.0 percent he owned previously.