Police confirmed they had received a report of damage to several headstones at the cemetery.
Inquiries into the incident were continuing, a spokesperson said.
Protective wrapping was placed over the headstones while restorations took place, but on December 6, further damage was discovered and left the Grave Guardians fuming.
Photos show polyester sheets over the graves, with massive rips in the centre and chips in the gold writing on the tombstones, which appear to have been covered in bleach again.
In a Facebook post, Grave Guardians said it was taking the continual damage “personally” and urged whoever was doing it to stop.
They described the vandalism as “deliberate and calculated”.
“The McLaren cluster of headstones just seem to be a magnet,” the Facebook post says.
“We have repeatedly arrived to continue work to find the wrapping lifted off and further attempts made on the stones. This hampers efforts to finish the work because we spend an hour or two having to fix the mess that undoes everything we had done.
“It’s no longer being considered a well-meaning but uneducated attempt, this is deliberate and calculated.”
An updated version of the post says someone did witness the latest attacks and information has been passed on to police.
The Herald has contacted the Grave Guardians and the Bruce McLaren Trust for further comment.
McLaren was one of New Zealand’s biggest names in motorsport, having won four grand prix between 1958 and 1970.
He started the McLaren Formula One team in 1963.