An advertisement for a furniture store named The Sofa King has been blacklisted for claiming its prices were "Sofa King Low".
The slogan - which has been used as the company's strapline since it began trading and appears on the firm's shop front and vehicles - sparked complaints to police in 2004, the advertising watchdog said.
It drew further criticism when it was used in a regional newspaper ad which has now been banned.
Three readers of the Northampton Herald and Post claimed the catchphrase was "offensive and unsuitable for general display" when it appeared in the paper on August 4.
The Advertising Standards Authority (ASA) upheld their objections.
"The ASA noted that the phrase 'Sofa King Low' used the advertiser's company name but considered that it could be interpreted as a derivative of the swear word 'f***', which consumer research had found to be a word so likely to offend that it should not be used in ads at all, even when it was relevant to the name of a product," the watchdog said.
"Because of that, we concluded that the slogan was likely to cause serious or widespread offence."
The Sofa King, based in Northampton, defended its advert.
"They said complaints made to Northamptonshire Police in 2004 were not taken further by the Crown Prosecution Service and that no complaints had been made direct to them," the watchdog said.
"They said the slogan simply used their company name to refer to pricing and that the words had not been changed or run together or punctuation used in a way that was intended to cause offence.
"They did not believe the slogan caused serious or widespread offence."