Created by ad agency WCRS, the TV advert featured The Royle Family actress Sue Johnston discussing her experience using the Sky+ service.
"I'm very lucky that I'm an actor and I've managed to make a living out of it, but I've kept very close to my roots. I live a very ordinary life. I am a simple soul as far as technology goes, but I can manage Sky+," she said in the ad.
"You just press the button and you can record a whole television series. It's just so simple. I say to everybody who's worrying about going digital, don't worry about it, get a Sky box, then it's done. So I will become digital without feeling any pain at all."
The ASA subsequently received two complaints from viewers about the suggestion that the switchover would be too complicated without Sky. The complainants also expressed concern that the ad could cause undue worry among older people about switching to digital television.
In response, Sky argued that the ad was merely created to deliver "a clear and reassuring message to viewers about the simplicity of installing and using Sky+".
The firm said that it wanted to highlight the Sky+ service to consumers who had not yet "gone digital" and that the ad never claimed Sky+ was the only service available for switchover homes.
A testimonial was further supplied by Johnston claiming that the ad merely reflected her own personal experience using Sky+.
The ASA noted that Johnston was likely to appeal to an older audience, but judged that her delivery was "down-to-earth rather than unduly anxiety-inducing".
However, the organisation said that the ad did promote Sky+ as the best way to "become digital", when in fact the features it offers are not "a necessary or an automatic part of switching to receive digital television".
The ad therefore gave a "misleading impression that digital switchover was likely to be more technologically complicated than it was without Sky".
"We also considered that the ad implied it was necessary to subscribe to those enhanced services in order to switch over to digital TV when that was not the case," the ASA concluded.
The organisation ruled that the misleading ad must not be broadcast again in its current form.