Dyson has had the TV ad for its premium Pure Hot + Cool fan banned, over concerns it could mislead viewers.
The advert, shown in April, pictured the mains-operated Pure Hot + Cool Fan in a family's open-plan flat.
The fan was shown from several angles - straight on, from the side and from above - with no cord or electrical outlet visible, the Advertising Standards Authority (ASA) said.
The next shot showed the fan in a different location on a light-coloured floor with a thin grey line leading into its base.
But one viewer to complained the ad gave the misleading impression that the fan was cordless.
Dyson said the fan was clearly shown as having a cord, which was distinguishable from both the floor and the rug.
It added that if it made a cordless purifier, it was "reasonable to assume" that this would be one of the key features it advertised.
Advertising clearance agency Clearcast said Dyson had invested heavily in cordless products, for example its vacuum range, "so one could be confident" that the firm would advertise any new addition to the range.
The ASA disagreed - saying "if the fan had a cord that plugged into the mains electricity, viewers would expect to be able to see it in those shots".
The watchdog agreed the final shot showed a cord leading from the base of the fan, although it was thin and grey on a light background and the same colour, thickness and approximately the same length as the edge of the carpet which appeared opposite it on the screen.
It said: "For those reasons, we considered that it could be easily missed and seen as part of the background by viewers.
"We concluded that, overall, the ad was likely to give consumers the misleading impression that the fan was cordless, and therefore that it breached the Code."
Banning the ad, the ASA told Dyson not to imply that its fans were cordless if that was not the case.
A Dyson spokeswoman said: "Dyson always works to ensure that advertising is clear and accurate. We therefore regret that a complaint has been received about this advert.
"However, in this instance, we disagree with the ASA's decision. We have begun a process of appeal against this ruling."
