‘Chainsaw’ vandals destroyed a pro-A27 bypass sign near Arundel on Sunday night, according to the group that put it up.
The sign had been installed on the western side of Arundel on the A27 approach from Chichester.
David Cooper, chairman of pro-bypass group OneArundel, said: “So much for democracy!
“Someone cut down one of our signs on the approach to Arundel with a chainsaw, and then destroyed it to make sure it couldn’t be re-used.”
The sign had read ‘Support the Arundel bypass’ and was one of two that the OneArundel group had paid for.
Mr Cooper added: “It’s hard to imagine anyone doing this other than anti-bypass campaigners.
“We have now removed the other sign to stop it suffering the same fate.”
The publication of three options for A27 improvement at Arundel has stoked a fierce debate that has been going on for decades.
Paul Dendle, Arun district councillor for Arundle and Walberton, said: “I condemn this act of criminal vandalism, it does no credit to the anti-road cause.
“I believe who ever did this has scored a massive own goal and strengthened residents’ opinions for an offline bypass”.
A consultation on the bypass runs until October 22.