Direction signs were pulled down and mud sprayed on roads by saboteurs targeting a popular New Forest sportive over the weekend.
It was the second time this year a Wiggle-sponsored sportive in the New Forest has been hit. In April, the New Forest Spring Sportive had signage removed and tacks spread on the road.
After the weekend's attack, Martin Barden of UK Cycling Events, which organised both sportives told the Southern Daily Echo: "I believe they were a handful of very passionate people who doing it with good intentions but were not going about it in the right way. There was potential for serious injury to cyclists."
The course had to be rerouted around the mud-spreading incident, said the paper.
Opposition to New Forest sportives is believed to lie in equine groups, motorists and residents opposed to the increasing number of cycle events in the national park.
Last week, the New Forest Verderers, who look after the national park's habitat and wildlife said they were forced to cancel a counting and controlling exercise of the New Forest ponies because it clashed with the the sportive on Sunday.