Apple chief executive Steve Jobs has detailed why he will not allow Adobe Flash software on mobile devices such as the iPhone, iPod and iPad.
The software is unreliable and not secure, he said in an open letter posted on Apple's website, pointing to security problems associated with Flash that were highlighted by a 2009 report from Symantec.
"We do not want to reduce the reliability and security of our iPhones, iPods and iPads by adding Flash," he said.
The letter is the first in-depth public statement by Apple discussing its position on Adobe's software since Apple imposed the ban in 2007, according to the New York Times.
He said the decision was based on technology issues and not an attempt to protect Apple's App Store, as charged by Adobe.
Jobs said the most important issue is the fact that the Adobe software is proprietary, saying Apple believes that "all standards pertaining to the web should be open".
Apple supports open standards on the web such as HTML5, he said, despite using proprietary operating systems on the iPhone and iPad.
Jobs countered Adobe criticism that Apple mobile devices cannot access "the full web" because 75% of video on the web is in Flash.
"What they do not say is that almost all of this video is also available in a more modern format, H.264, and viewable on iPhones, iPods and iPads," he wrote.
The impact of Flash on mobile battery life and the fact that it is not designed for touch-screens, were the other main technical issues highlighted by Jobs.
"Even if iPhones, iPods and iPads ran Flash, it would not solve the problem that most Flash websites need to be rewritten to support touch-based devices," he said.