A Manchester United fan was told by police she faced legal action unless she removed part of a car sticker which teased Manchester City.
Sarah Webb-Lee, 39, sported a sticker on the rear window of her Vauxhall Corsa which read: "On the first day God created United then completely fucked up and created City."
A local councillor passed on to police a complaint they had received from a resident about the wording of the joke and a neighbourhood team officer was sent to the motorist's home in Stockport.
Mrs Webb-Lee and her City-supporting husband Graham were informed that the sticker was offensive under the terms of Section 5 of the Public Order Act. They were asked to either remove it or some of the letters within the swear word, and they did the latter.
Mrs Webb-Lee told the Manchester Evening News: "I couldn't believe it when the police turned up. It was just a bit of a laugh. We don't have many rights left but freedom of speech is worth hanging on to. I won't take it down.
"It's just a bit of banter and you hear worse on the terraces. I see lots of things about United and take it on the chin."
Inspector Stephen Gilbertson said: "We received a complaint about the language contained in a car sticker that, by law, is offensive.
"All we did is make the relevant people aware and asked them to either remove the sticker or some letters within the swear word, which they willingly did.
"It is important to stress this had nothing whatsoever to do with any football team and was solely in relation to an offensive word."