In a short letter to the board of Apple, Mr Jobs wrote: "I have always said if there ever came a day when I could no longer meet my duties and expectations as Apple's chief executive, I would be the first to let you know.

"Unfortunately, that day has come. I hereby resign as chief executive of Apple.

Apple founder Steve Jobs has resigned as chief executive of the technology giant and will be replaced by its chief operating officer Tim Cook.

Mr Jobs, who underwent a liver transplant following pancreatic cancer, said he could no longer meet his chief executive's duties and expectations.  Steve Jobs will become chairman of the firm.