The iPhone 4 can multitask, there is no questioning that.

Steve Jobs, CEO of Apple, has personally shown us, at length in two press announcements, that it can. He demoed the function at the launch of the new iPhone OS and again at WWDC10, and proved that you will be able to switch between multiple apps on the phone.

We've also tried it here in the Pocket-lint office thanks to a play with the latest GM build of the iOS 4 update on an iPhone 3GS.

But here's the rub: Currently, in our initial testing, only Apple apps, like the Clock, Mail and Safari, can multitask. That's it!

It seems that, as Jobs pointed out, developers will need to enable multitasking on their apps for the function to work, before it comes with the free iOS 4 update on June 21. Something that's unlikely in a vast number of cases. 

When we spoke to a number of developers, that aren't keen to be named in this article for fear of backlash from Apple, they all confirmed to Pocket-lint that, for any app to take advantage of the new multitasking features, it will have to be updated. Furthermore, many of those we spoke to felt that many apps simply won't be.

"Why would you want to multitask during a game," explained one.

Another said that, "the way Apple is marketing it is a bit misleading. Out of the 200,000 apps available, only a few will be able to multitask, and possibly not from day one." 

We also spoke to TomTom, who confirmed that while its own app will be able to multitask from the off, it hinted that every app developer needs to submit a new, updated build, which must then be approved by Apple: "We will be submitting our app on June 21, to bring iOS 4 users the chance to multitask once the app is approved by Apple," TomTom's UK PR Manager Rosie told us.

The news is likely to come as a massive shock to current and new iPhone customers, who will no doubt expect to be able to multitask any app from day one.

It also means that if you do want to multitask, you might not be able to with your favourite apps until that developer updates them.

Judging by some app developers' update schemes, and the fact that some do it for love rather than money, that might be a very long time.

We've currently tested the feature with over 50 apps, such as games like DoodleJump, Skype, IMDB, Sonos and many more, and, as yet, not got it to work effectively.

So, either you'll be having to download a lot of new updates come 21 June (or around 24 June, when your brand new iPhone 4 arrives) or Apple's flag waving multitasking feature won't be coming to the iPhone iOS 4 platform quiet yet.

We are awaiting comment from Apple. However, it seems that iPhone 4 and iOS 4's multitasking functionality is now in the hands of the app development community, all 200,000 of them.

To give you some further background on multitasking; the new feature will see a dock appear from the bottom of the phone after pressing the home screen when you want to switch to another app, in an interface that is reminiscent of adding widgets to the Dashboard feature in Mac OS X.

Apple has said at previous events that it is not an open range for developers to go wild and that they will only offer seven types of multitasking, like audio, location, and notifications, which it believes will be enough to give users what they want.

The Seven types will be:

Background audio - Allows your app to play audio continuously, so customers can listen to apps while they surf the web, play games, and more.

Voice over IP -  Users will be able to receive VoIP calls and have conversations while using another app. They can even receive calls when their phones are locked in their pocket.

Background location - Navigation apps can now continue to guide users who are listening to their iPods, or using other apps. iPhone OS 4 also provides a new and battery efficient way to monitor location when users move between cell towers. 

Push notifications - Receive alerts from apps even when an app isn't running.

Local notifications - Apps can now alert users of scheduled events and alarms in the background, no servers required.

Task finishing - If an app is in mid-task when your customer leaves it, the app can now keep running to finish the task.

Fast app switching - Allow users to leave an app and come right back to where they were when they left - no more having to reload the app.

Apple has demoed the new feature with a number of third party applications including Skype, US music service Pandora, and GPS apps like TomTom, none of which are currently available to iPhone users.

Catch up on the rest of Pocket-lint's extensive iPhone 4 coverage on our dedicated iPhone 4 hub.