Apple is set to unveil a new ultraportable laptop on January 15, according to the army of online pundits dedicated to tracking the iPod maker’s every move.

MacWorld, the company’s annual jamboree, is still two weeks away, but already the web is buzzing with details of expected new products and business partnerships – including a series of deals with Hollywood studios under which Apple will enter the online rental video market, and a rumoured upgrade to the iPhone that would give the device a GPS-type function.

However, the expected launch at the San Francisco-based event of a lightweight, super-thin laptop – a device seemingly pitched between the iPhone and its current MacBook line of computers – is kindling the greatest interest among Apple aficionados.

Suggestions that such a machine, said to be fitted with flash-based memory and an external disk drive, is imminent were stoked last month when digitimes.com, the industry site, revealed that Apple has secured a supply of 13.3-inch LED backlight units, used for ultraportable computer displays, from Taiwan.

Commenting on a proliferation of more detailed reports in recent days, engadget.com , the closely-read blog, said: “While anything is obviously possible, it sure seems like the safe bet is that Apple will unveil some form of ultraportable laptop at MacWorld in a couple of weeks.”

Mac Rumors, another website, said it had received "reliable confirmation" on a number of features of Apple’s forthcoming “sub-notebook” including the omission of an internal optical drive to cut down on size and weight.

“Instead, Apple is said to be offering an external optical drive with the sub-notebook. This detachable external drive would allow customers to read/write from CDs or DVDs as usual, but would allow users to leave this extra bulk at home when on the road,” the site said.

It added that Apple is also expected to announce upgrades to its current line of MacBook and MacBook Pro computers.

The rash of speculation suggests that Apple is fighting a losing battle in its efforts to clamp down on the leaks and speculation that accompany its product launches. Last month it reached a legal settlement with Think Secret, a site it had sued for allegedly leaking industrial secrets.

The addition of a new ultra-portable machine would fit with Apple’s recent thinking. The iPhone, which comes equipped with a fully-fledged web browser, was heralded as much as a miniature computer as a telephone when it was revealed at last year’s MacWorld.

Apple also has close links with Google, which is bidding for a spectrum license in the US that could be used to roll-out a wireless broadband network.

Rival internet players such as Yahoo, meanwhile, believe that more people will soon access the internet through mobile devices than through conventional computers.

The launches of iPod models, and more recently of the iPhone, have garnered the bulk of the media coverage lavished on Apple, but the company’s computer business has also made great strides.

In its latest financial statement, Apple said that it sold a record 2.16 million Macintosh computers in its forth quarter, 34 per cent than for the same period the year before. Of those, sales of laptops rose 37 per cent, contributing to a 67 per cent leap in profits to $904 million (£445 million). The news helped push Apple shares above $200 for the first time.

Recent surveys suggest that the company has since continued to make up ground on the PC.

According to Net Applications, a group that tracks internet use, more than 7 per cent of visits to websites in December came from Apple’s Mac computers, a record high. Computers powered by Microsoft’s Windows operating system still dominated, however, accounting for more than 90 per cent.

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