Apple has ramped up the pressure on RIM, the BlackBerry maker, by announcing that the iPhone will now be able to link up with corporate e-mail systems, making it more attractive to business customers.

Steve Jobs, Apple's chief executive, also made a bid to widen the iPhone's appeal by allowing software developers to write applications for the device, meaning that owners will have a broader range of features to choose from.

Until now, many businesses have shied away from giving their executives iPhones because the device did not synchronise with the Microsoft's widely used e-mail program, Exchange, as the BlackBerry device does.

Mr Jobs said that the new business features, which also include enhanced security such as the ability to lock the device remotely in the event of theft, would be added in June, and would be available as a free software upgrade to existing owners.

Apple also made a bid to turn the iPhone into a platform for third party applications by releasing a software kit that will enable developers to write programs for the device. For $99, developers will be able to download software that will let them write anything from games to financial applications that iPhones owners can in turn install on their devices.

So far, iPhones have only been able to run a limited number of applications developed by Apple.

"We're very excited about this," Mr Jobs said at an event in Cupertino, California. "“We think a lot of people, after understanding where we are going, are going to want to become an iPhone developer.”

The new applications will be available exlusively to iPhone users through an online shop called 'Apps Store'. Apple said it would keep 30 per cent of the sale price, and would also retain the right to reject applications that included inappropriate elements, such as pornography.

Sega, the game manufacturer, and AOL, the internet portal, are among the companies who have already created applications for the iPhone using Apple's new software kit.

John Doerr, the venture capitalist, also announced that his firm, Kleiner Perkins Caufield & Byers, would establish a $100 million fund specifically to support iPhone developers.

"The potential for iPhone is huge," Mr Doerr said, adding that the fund - called the iFund - was the largest his company had created for a single technology.

Separately, the BBC announced today that the iPlayer, which allows viewers to stream or download BBC shows from the internet, was now available on the iPhone.

The BBC's head of digital media technologies, Anthony Rose, said that Apple's device had been chosen because it was the "most optimised" of the current handsets for high quality video, but that the iPlayer would soon become available on other phones, including Nokia's N95.

The iPhone and the iPod touch needed to be connected to wi-fi networks in order to stream or download programs using the iPlayer, Mr Rose said.

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