The Advertising Standards Authority (ASA) has widened its inquiry into Apple following new complaints about the capabilities of its latest iPad, it said.
The regulator confirmed a BBC report that it is investigating "potentially problematic" claims on Apple's website about the iPad's 4G capabilities in the UK.
The UK does not yet have widespread 4G coverage, and the iPad will be incompatible with it when it does.
The ASA said it first approached Apple after receiving 40 complaints about "potentially misleading" 4G claims but closed the case informally when the company agreed to change its advertising.
It is now investigating new complaints from consumers that suggested the problematic claims were still appearing.
Apple has so far declined to comment. However the BBC reported a source at the company saying that no undertaking was given to remove all references to 4G from its site.
Apple's UK site still allows consumers to buy a "Wi-Fi + 4G" version of the iPad.
The ASA said in a statement: "To confirm, we received 40 complaints about claims for the iPad with Wi-Fi and 4G that appeared on Apple (UK) Ltd's website. Complainants challenged whether the references to 4G were misleading, because they understood that 4G was not currently available in the UK. Some of the complainants also challenged the description of the iPad as 4G because they did not believe that the iPad would be compatible with 4G networks when they were introduced in the future.
"When we approached Apple with the concerns that had been raised, it stated it had removed references to 4G from the webpage that was subject to the complaints. Apple also agreed to edit a video that contained references to 4G. On the basis that the issues that had been raised with us had been resolved we closed the case informally.
"We have since been contacted by several complainants who have identified other potentially problematic claims about the iPad and 4G on Apple's website. We are currently assessing these new complaints. If it appears that the problem claims we asked Apple to remove are still appearing, we will investigate these new complaints."