Vandals have daubed “Welcome to Hell” on the Sheppey Crossing.
It appears in foot-high black lettering on a pillar beside a gold plaque marking the bridge’s opening.
On another concrete support, the words “Turn Back Now” have been painted.
Both items of graffiti are easily visible to motorists driving along the Sheppey Way towards Kingsferry Bridge.
Islander Helen Edwards, 42, who spotted the damage this morning, said: “I’m really shocked - it’s so in your face.
“It doesn’t make a very nice impression for people who are travelling to the Island for the first time.
“They’re going to think,’What sort of place is this’?
It is not known when the graffiti first appeared, but Swale council was alerted and a team has been dispatched this morning to remove it.
Heather Thomas-Pugh, chairman of Sheppey Tourism Alliance, said she hadn’t seen the crude markings, but added: “This is a beautiful island and it certainly isn’t hell.
“We’ve got so much to offer in the way of tourism. We’ve got a vast amount of history, heritage and culture.
“In fact, it’s a paradise rather than a hell.”
Mrs Thomas-Pugh said she was stupefied by the vandalism.
“I can’t understand why people have to do this sort of thing when we’re trying to raise the Island’s economy and put it on the map.
“These vandals are trying to make some sort of statement and it’s an absolute load of rubbish.”