The TV ad for promoting the retailer's bed sale received 30 complaints from viewers who objected that the ad was likely to encourage dangerous behaviour because they believed it showed the man using his mobile phone while in control of a vehicle.
The spot began with a man leaving his house to go to work, while a woman in bed was taking a picture of herself on her mobile phone.
The man was then shown sitting in the driving seat of his car, framed in the wing mirror, with his mobile phone in his hand.
The ad cut to a shot of the man's hand holding his phone, which displayed the picture of the woman in bed with text underneath saying "Day off xxx".
It then went on to show and describe several products that were on sale.
Sleepmasters said that it was aware of the legal and social ramifications of the use of mobile phones and they had therefore shot the scene on the driveway of the house where the car was stationary.
Clearcast believed the car was obviously stationary and pointed out that the man stepped into his car as he was receiving the text message. It said that the car was parked on the drive and the ad clearly showed a patch of grass and a parked car opposite the man's car.
The Advertising Standards Authority noted Clearcast and Sleepmasters' responses, but said that the man was sat in the driving seat of his car when he read the text message.
It considered that it was not clear whether the man was in control of the vehicle when he was using his mobile phone and concluded that, because of the ambiguity, the ad could encourage or condone dangerous and irresponsible driving and the use of mobile phones while driving.
The ASA upheld the complaints and ruled that the ad must not be shown again in its current form.