Campgrounds can ask them to cover up but can't ban Wicked Campers.

A mysterious spray-painting vigilante is covering up offensive slogans on Wicked Campers vehicles.

The undercover cover-ups have seen at least four of the controversial company's campervans sprayed over as they travelled up the West Coast.

Murchison's Riverside Holiday Park, leaseholder Robin Sandford said the last four Wicked Campers vehicles that had stayed at his park were spray-painted over.

FIONA GOODALL/GETTY IMAGES The Tasman District Council recently discovered it could not ban Wicked Campers from its four campgrounds.

"Somebody has been painting them up and most of them have been coming from the West Coast. The last one said it was done in the parking lot of the Swing Bridge in the Buller Gorge and another one in the New World in Westport," he said.

READ MORE:

* Wicked Campers banned at Kaiteriteri

* Wicked ban boosts business

* Tasman District Council looks into banning Wicked

* Wicked Campers could face big company wrath

* 'Bit of sexual violence never hurt anyone'

* Wicked Campers draw heat in Taupo

"It's not the owner, it's somebody else from the general public and they're getting grey spray-paint — it's not messy, like a kid would do it — it's over the offensive words. I could tell what was greyed out and it was bad."

Getty Images One motor camp manager uses tape to cover over any offensive material.

However, Sandford, who leases the park from the TDC, thought the issue wasn't as big as it was made out to be.

"I think it's offensive, for children for sure but I think it's a little bit of a storm in a teacup. With all the other problems we have with freedom camping right now, I think there's other issues that should be addressed."

The cover-ups have emerged as the Tasman District Council discovered it could not ban Wicked Campers vehicles from its four campgrounds.

GETTY IMAGES Vans at Wicked Campers depot in Penrose, Auckland.

Deputy mayor Tim King said the council's legal advice suggested it would be difficult to enforce a ban against a single campervan company, and the council would need to change the lease agreements with its private camping operators to enforce a ban.

However, at a council meeting last week he said that stance was unnecessary, as operators were refusing to admit vans with offensive signage already, or insisting any distasteful slogans were covered up..

Outside the meeting, King said he supported how the operators had decided to address the matter.

"I think it's an appropriate way to deal with the issue really, not over the top and doesn't require any specific rule changes or anything. It's just them using their discretion to decide what they want in and out of their camps."

Golden Bay's Collingwood Motor Camp manager Chrissy Clements said she and her husband Gary had been policing the vans "pretty much since we started". This was before the council had asked for a ban on the controversial campers.

"It's the really offensive ones, ones that are derogatory against women. Guests have complained about it before," she said.

"We know that Wicked won't do anything about it, so it's up to us."

Clements uses tape to cover over any offensive material, if tourists with Wicked Campers want to stay with them.

"Reactions haven't been too bad, it's not the campers fault that they have that van, sometimes that's the only van left and it's either that or nothing," she said.

Although the motor camp only sees "about half a dozen a month", they are in full support of the council.

"We aren't keen to have that sort of carry on about that sort of thing [the offensive slogans], we're a family park. It's not on," she said.

The Kaiteriteri Beach Motor Camp banned Wicked Campers from their grounds in March, which received a positive response, manager Dennis Petch said.

"We're probably getting more [business] from campers coming in just to support us than the ones we've lost, but that's not why we did it."

King believed change would only happen if tourists stopped using the vans.

"At some point the only thing that is likely to change is the market so if people stop hiring them, they'll probably change," he said.