Sixty-seven year old Roger Simpson spotted the artwork while walking down Union Street in Dewsbury a few weeks ago.
The painting stood out to Roger because the artwork of Charlie Chaplin and a young child was painted in a Banksy style.
But the artwork has now been defaced with obscene images - leaving the painting unrecognisable.
Roger said: “It's a real shame and whoever painted it must be devastated because it is a good piece of work.
“If it is a Banksy artwork, how is he going to feel?
“If I had painted it I would be really disappointed that someone has vandalised it.
“It is weird that they have done this now - I don’t understand why they have done such a thing.
“I went and asked the business - Lee's Traditional Fish and Chips - in which the painting is on if they had anyone come in and ask for permission and they said that no one had been in and asked.
“It’s still a mystery and I am no expert at all.”
In a letter to the Dewsbury Reporter, Hilary Trotter believes more police are needed in the area to deter vandals from doing things like this in the future.
She said: “The wall painting on Union Street lasted just 24 hours before somebody decided to spray an obscene gesture in red paint - this just sums up what Dewsbury has to contend with.
“We need more policing to move vandals on.”