Millions of consumers have downloaded a Skype Web telephony application that launched Sunday, allowing users of Apple Inc iPhone to use privately held Skype's service over the cellular network for the first time, a Skype mobile executive said on Wednesday.

Before the launch of the application for use on high-speed third generation (3G) networks on May 30, consumers could only use Skype on their iPhone when they had access to Wi-Fi, a short-range wireless technology found in venues like coffee shops, homes and offices.

We've had millions of downloads to date, Russ Shaw, Skype's general manager for mobile, told Reuters. That's really positive.

However, Skype faced a lot of complaints from Web commentators after it also said on Sunday that it would start charging for 3G calls between Skype users next year.

This was seen as a big turnaround since the main reason Skype became popular was that Skype-to-Skype calls have always been free whether subscribers use it on their computer or their cellphone.

Shaw said the company needs to start charging for the service so that it can fund the investments needed to ensure that the quality of 3G Skype calls stays high.

He declined to give specific details about pricing plans except to say that the service would still be competitive with rival services including traditional cellphone calls.

We're not going to want to price ourselves out the market, he said. I can't ignore the fact that consumers (currently) use us for free.

(Reporting by Sinead Carew; Editing by Phil Berlowitz)