A Northern Territory councillor has trademarked graffiti that reads “Jesus loves nachos”.

Toni Tapp Coutts, an author and Katherine town councillor, spent months obtaining the legal protection for the slogan that she says could help tourism and souvenir sales.

“It’s three words but I thought they were important enough to trademark and make the story tangible,” she said.

The text appears on the side of a rusty bridge near the rural town, and is already part of local folklore, appearing on car wrecks, tea towels and even tattoos.

Cr Tapp Coutts admits that a member of her family wrote part of the slogan, but would not reveal who.

“This is how it started apparently: in the mid to late-80s some Aboriginal boys from Barunga community were in Katherine on a Christian convention and they wrote ‘Jesus loves’ on the bridge,” she told reporters.

“Then in the early 90s someone added ‘nachos’. Because it seemed like a good thing to do, obviously.”

The bridge on which it is written is heritage-listed, meaning restoring it would be challenging.

“It’s really, really faded now, so I wanted to trademark it as a way of keeping it alive,” Cr Tapps Coutts said.

Some locals, Christian groups in particular, are not thrilled about the line, but this is not the first time efforts have been made to protect it.

A 2016 planning document on structural upgrades to the bridge came with very specific instructions.

“‘Jesus loves nachos’ is not to be touched,” a spokesperson for the NT Government’s infrastructure, planning and logistics department told the Katherine Times.

“It’s an icon.”