Lorraine Watson, 54, is furious after being told by a local council she must remove the sign - despite it become a tourist attraction in its own right.
The Carron Fish Bar in Stonehaven, Aberdeenshire, is credited with being the first place to deep fry a Mars bar - a greasy treat which has become a world famous delicacy.
The £1.50 snack has become synonymous with negative aspects of the Scottish diet since it was “invented” in the mid-1990s.
And as part of improvements to the town, council chiefs have written to Lorraine asking her to remove the banner “for the good of the wider community”.
But Lorraine, who has owned the shop for two and half years, branded the move “silly”.
She said: “I just think it’s silly. It’s wrong in asking me to take it down. My issue is there’s nothing wrong with the banner, it’s not ripped and messy or anything.
“It’s actually an icon for the town. Thousands of people come from all over the world to get a Mars bar and get their picture taken below the banner.
“I can’t see what the council’s problem is. It’s actually bringing tourism to the town. I certainly won’t be doing it.”
The banner has been above the shop since 2006, long before Lorraine took over the business.
And she said she has received thousands of messages of support from friends and locals, backing the banner.
She has also just spent £80,000 refurbishing her business, making her fume even more over the council’s suggestion.
Aberdeenshire Council’s letter states: “What needs to be done: Remove banner. We would like you, for the greater good of the wider community, to consider doing this work.”
Lorraine added: “When I read the letter I was like, ‘Oh my God, are you joking me?’
“There are other things to be addressed in the town other than this banner. It’s doing no harm.
“We’re meant to be advertising Scotland and promoting tourism. It’s about bringing people here.
“The support I’ve had in the past 24 hours has been incredible.”
A spokesman from Aberdeenshire Council said: “Together with a range of community organisations we have been looking at ways to improve the look of Stonehaven for the benefit of residents, businesses and visitors.
“An action plan has been created in conjunction with the Stonehaven Town Partnership, Community Council, Stonehaven Business Association and the Horizon Group.
“As part of the action plan we have asked some owners in the area to consider making alterations to their properties.
“This included asking the owners of The Carron Fish Bar to consider removing their banner.
“We do not wish to prevent the owners from promoting their business and we would be happy to have discussions with them regarding the banner.”