Apple has fallen foul of UK advertising regulations for exaggerating the speed of its hugely popular new iPhone.

The Advertising Standards Authority (ASA) upheld complaints about a television ad for the iPhone 3G which boasted of the gadget's "really fast" performance.

The ad stated: "So what's so great about 3G? It's what helps you get the news, really fast. Find your way, really fast. And download pretty much anything, really fast. The new iPhone 3G. The internet, you guessed it, really fast."

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The ad showed a close-up of the handset being used to surf a news webpage, view the Google maps service and download a file, with the user waiting just a fraction of a second for each action.

Text on the screen said: "Network performance will vary by location.".

The ASA said 17 viewers complained that the ad was misleading because it exaggerated the speed of the iPhone 3G.

It upheld the complaints, ordering that the ad must not appear again in its current form.

Defending the ad, Apple UK said it was intended to compare the new 3G model with its 2G predecessor, and the claims were "relative rather than absolute in nature".

As such, the implication that the 3G iPhone allowed "really fast" downloads and internet access in comparison to the previous generation was not misleading, it said.

The company said the average viewer was a mobile phone user and would have understood that a device's performance varied due to several factors.

It also claimed that the average viewer would understand that a 30-second TV ad was simplified to allow an illustration of the device, adding that the text stating "network performance will vary by location" underlined the possibility of performance variations.

But the ASA said many viewers might not be fully aware of the technical differences between the new iPhone and its predecessor and noted the ad did not give an explicit indication of a comparison with the older phone.

It said the ad was likely to lead viewers to believe that the device actually operated at or near to the speeds shown in the ad.

It concluded: "Because we understood that it did not, we concluded that the ad was likely to mislead."