Many manufacturers, including Samsung, plan to launch tablet computers in the next six months and take on the market cornered by Apple's iPad.
But Jobs claimed that the seven-inch screen of those tablets so far announced would be too small for consumers to operate easily.
He said, "We think these seven-inch tablets will be dead on arrival. They'll learn the painful lesson that they're too small and have to expand them next year."
"You might think a seven-inch screen would have 70 per cent of the size of a 10-inch screen [such as that of the iPad], but that measure is diagonal. In fact, it’s only 45 per cent of the area of an iPad screen. If you take an iPad and draw an imaginary horizontal line halfway along, that’s the size of a seven-inch tablet display."
Jobs added, "The only way they’re going to sell is if they come with sandpaper, because you’re going to have to sand people’s fingers down so they can work it. You can’t run the software you need on a screen that small."
He also said that the existence of numerous online Android stores would make it much harder for developers to distribute apps, than it is through Apple’s single iPhone and iPad store.
And the reason that PC manufacturers had so far failed to take on the iPad was down to their lack of specialist knowledge. "We’ve done everything from the iPad’s A4 processor to the battery chemistry," said Jobs.
"We’ve learned a lot from the miniaturisation on iPods and iPhones. We’re a very large-volume consumer electronics manufacturer. We’re system architects, we know how to make products in an interesting way. This is a product we’ve been preparing for the past decade."
Jobs was speaking to analysts on the day that Apple revealed its latest quarterly profits were up 70 per cent year-on-year to US$4.31 billion, thanks to the sale of 4.2 million iPads, 14.1 million iPhones and 3.9 million Macs.
He boasted that Apple’s iPhone was now more popular than Research in Motion's BlackBerry (based on the latter's most recent quarterly sales of 12.1 million phones).
RIM also plans to take on the iPad and unveiled its seven-inch PlayBook in September.
In response to Jobs' comment, Jim Balsillie, co-CEO at Research in Motion, said, "For those of us who live outside of Apple’s distortion field, we know that seven-inch tablets will actually be a big portion of the market and we know that Adobe flash support actually matters to customers who want a real web experience."
"We also know that while Apple’s attempt to control the ecosystem and maintain a closed platform may be good for Apple, developers want more options and customers want to fully access the overwhelming majority of web sites that use Flash."
He added, "We think many customers are getting tired of being told what to think by Apple. And by the way, RIM has achieved record shipments for five consecutive quarters and recently shared guidance of 13.8 to 14.4 million BlackBerry smartphones for the current quarter."
Balsillie goes on to say that Apple’s comparison of its September-ending quarter with RIM’s August-ending quarter does not tell the whole story.
"It doesn’t take into account that industry demand in September is typically stronger than summer months, nor does it explain why Apple only shipped 8.4 million devices in its prior quarter and whether Apple’s Q4 results were padded by unfulfilled Q3 customer demand and channel orders," he said.
He added, "As usual, whether the subject is antennas, flash or shipments, there is more to the story and sooner or later, even people inside the distortion field will begin to resent being told half a story."
Jobs' criticism was not restricted to his rivals’ tablet plans. He also said that Android’s use on more than 100 handset models meant that its performance would be inconsistent across different handsets.
He also condemned Google’s previous insistence that its Android software was "open" and that Apple’s was "closed", describing Google's words as a "smokescreen". He added that Apple’s integration of hardware with software made its products more effective.