In a surprise post on Apple’s Web site, CEO Steve Jobs has defended his company’s decision to block Adobe’s popular media playback software Flash.

Jobs said he wrote the post because he wanted customers and critics to “better understand why we do not allow Adobe’s Flash products on iPhones, iPads and iPods.”

“Adobe has characterized our decision as being primarily business driven — they say we want to protect our App Store — but in reality it is based on technology issues,” he said. “Adobe claims that we are a closed system, and that Flash is open, but in fact the opposite is true.”

Ever since Apple (NASDAQ: AAPL) made clear that it wouldn’t support Flash on the iPhone, reports have swirled alleging bad blood between the two firms. Jobs was reported to have called Adobe “lazy” at a company meeting and characterized Flash as buggy, slow and a security threat.

Critics have charged it’s more of a control issue, that Apple wants to limit the core software on the hot-selling iPhone and the new iPad to what it develops in-house and to open standards like HTML 5, in the process choking off a competitive threat to its iTunes store. Adobe (NASDAQ: ADBE) went so far as to develop a workaround it thought would make Flash more palatable to Apple, but right before its release Apple changed the iPhone developer guidelines, limiting what tools developers could use for iPhone apps and effectively cutting off Adobe’s solution as well as several other developer tools.

Adobe did not respond to a request for comment by press time, though the company said earlier this month that is has no plans to do any further development work to get Flash on the iPhone.

In his post, Jobs called Flash-based products “100 percent proprietary,” arguing that Adobe keeps a tight lid on their development and market availability.

“They are only available from Adobe, and Adobe has sole authority as to their future enhancement, pricing, etc,” he said. “While Adobe’s Flash products are widely available, this does not mean they are open, since they are controlled entirely by Adobe and available only from Adobe. By almost any definition, Flash is a closed system.”

Jobs conceded Apple is no stranger to proprietary products. But while the operating system for the iPhone is proprietary he said that Apple “strongly believe(s) that all standards pertaining to the Web should be open.” He noted that Apple has opted for open standards such as HTML5, CSS and JavaScript over Flash.

“HTML5, the new Web standard that has been adopted by Apple, Google and many others, lets Web developers create advanced graphics, typography, animations and transitions without relying on third-party browser plug-ins” like Flash, he said. “HTML5 is completely open and controlled by a standards committee, of which Apple is a member.”

Jobs also noted that Apple has contributed to the “open” Web with projects like WebKit, a complete open source HTML5 rendering engine used in its Safari browser, as well as Google’s Android browser. Palm has also used WebKit, and RIM plans to tap the project for the next version of the BlackBerry operating system.

“Adobe has repeatedly said that Apple mobile devices cannot access ‘the full Web’ because 75 percent of video on the Web is in Flash. What they don’t say is that almost all this video is also available in a more modern format, H.264, and viewable on iPhones, iPods and iPads,” Jobs said. “YouTube … an estimated 40 percent of the Web’s video, shines in an app bundled on all Apple mobile devices, with the iPad offering perhaps the best YouTube discovery and viewing experience ever.”

But his post elicited a pointed and detailed response from Lee Graham, co-founder of TRImagination.

“As a Flash developer, I feel Mr. Jobs’ arguments are fairly weak. First and foremost, there is a huge difference between developing apps and developing Web sites that are viewed on mobiles. Steve kind of blurs the two together throughout,” Graham said in an e-mail to InternetNews.com.

“Adobe Flash runs within browsers, while Adobe AIR has been used to develop desktop and native mobile apps which includes iPhone and iPad apps,” Graham added. “While Flash hasn’t been tested in the iPhone Safari browsers, there are over 100 apps that were built with Flash CS5 and AIR 2 that are currently in the iTunes Store.”

He also argued that HTML5 is “nowhere to being complete and it simply doesn’t have the capabilities of Flash.”

Google, a strong supporter of HTML5, recently confirmed that it’s working closely with Adobe to bring Flash to Android-powered mobile devices. There are already several Flash applications available for Android.

But Jobs insisted Flash is a relic of the PC age that isn’t tuned to perform in the mobile era of low power devices, touch interfaces and open Web standards.

Meanwhile, analyst Phil Leigh, who publishes the “Inside Digital Media” newsletter, thinks Adobe faces a bigger problem than losing the iPhone.

“I think this signals the end of Flash as a successful platform,” Leigh told InternetNews.com. “HTML5 or whatever Apple advances is going to win because they are the most influential force in digital media today.”