Grangemouth Councillor David Balfour and the Friends of Rannoch Park are furious at the sudden appearance of a large painted logo with the letters BNK on the park’s pavilion.
It was recently decorated with murals designed by Carrongrange High School pupils.
The eyecatching murals were painted on to the pavilion by a local atist, helped by Grangemouth High pupils - but another “artist” has now covered a whole gable wall with graffiti.
Councillor Balfour said: “Myself and the Friends of Rannoch Park group have worked very hard over the past few years with local primary and high school children and volunteers from the community, some with a range of disabilities, to improve the park.
“The park is now used by many local residents of all ages and abilities and is a fantastic asset to the local community”.
He added: “I am extremely saddened and angered that someone would deface the pavilion wall in an act of mindless vandalism. “Someone out there must have seen this happening or know who has carried out this despicable act.
“I have contacted Police Scotland and the Community Safety Team and I am seeking the help of the public to find those responsible. I would urge anyone with information to come forward.
“Although disheartened by this incident, we will continue to make improvements to the park and strive for access for all.”
William Martin, secretary of the Friends of Rannoch Park, said: “We are very dismayed and shocked that the hard work we have put in with the assistance of Councillor Balfour and local children and adults has been tarnished in such a way.
“Those responsible perhaps have family and friends that use the park.
“This is a terrible, thoughtless act of vandalism.
“We have ongoing improvement plans for the park and will continue to work on these for the benefit of the local community”.