The adverts, which ran in January, featured Jamaican athlete Bolt mimicking Virgin Group founder Sir Richard Branson.
Sitting behind a desk he said: "Hi I'm Richard Branson and I want everyone to say bye-bye to buffering and hello to a superfast broadband."
A voiceover then stated: "Right now with Virgin Media you could enjoy up to 30 meg fibre optic broadband and calls free for the first three months and, with broadband that's four times faster than the UK average, everyone at home could be online at the same time."
However, rival internet service provider BT challenged whether the claim "say bye-bye to buffering" was allowable, as it may have "misleadingly implied" that Virgin Media broadband customers would not experience buffering, whereas BT "understood that was not the case".
Virgin Media accepted that there were "numerous cases of buffering" on its network, but claimed that some of these were outside of its control.
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The cable operator said that the claim made by Bolt about buffering was "puffery", and the sprinter, assuming the character of Branson, was merely "expressing a wish that he would like everyone to be able to say bye-bye to buffering and not claiming that they actually would".
Virgin claimed that buffering on its up-to-30Mbps broadband service was "less discernible", but also noted that the ads were no longer running and would not be aired again.
In a ruling today (July 25), the Advertising Standards Authority (ASA) said that the statement "I want everyone to say bye-bye to buffering and hello to a superfast broadband" would "be interpreted by viewers as an objective claim that, by choosing the up-to-30 Mb broadband service from Virgin, they would no longer experience buffering".
As the ASA noted that some users of the service might still experience buffering, it concluded that the claim was "misleading".
Virgin was told by the watchdog that it must not "state or imply that users of their broadband service would not experience buffering" in any future ad campaign.
In April, Virgin Media agreed to drop a different television advert featuring David Tennant after a complaint from the BBC that the Doctor Who brand was being used to promote the TiVo set top box service.