Access to Lake Rotomā is being blocked after four-wheel-drive vehicles have continued to drive across the lakebed despite the environmental damage.
Te Arawa Lakes Trust environment manager Nicki Douglas said she was saddened by the damaging activity.
"Restoring our lakes and surrounding environments is a legacy we take pride in and the behaviour continues to go against the hard work everyone is doing for the wellbeing of our lakes, waterways and lakebeds."
Douglas said the risk of vehicles spreading weeds and catfish is high.
Access has been blocked at Rotomā Rift Valley and further barriers will be placed to stop four-wheel-drive and vehicle access to the foreshore and lake.