Around 1,700 signs enforcing Westminster Council's motorbike parking charges have been vandalised.
Since 2008 motorcyclists have been charged £1 per day to park in the borough, leading to regular protests by the No To The Bike Parking Tax group.
Referring to the signs, it said on its website: "Do not pay the parking tax if the bay is obliterated, the bay is non-enforceable and therefore free."
Westminster said their signs provided "vital information".
Now the authority is vowing to monitor "trouble spots" in an attempt to catch the culprits.
Council officers say they have seen statements on the internet referring to the attacks as "liberating bays" and urging motorcyclists to "fight back now".
Dr Leith Penny, Westminster council's director of city management, said: "This criminal damage has been carried out by vandals who appear to think they are above the law.
"We will not hesitate to prosecute any individuals found to be carrying out action that is tantamount to stealing from the public purse."
No To The Bike Parking Tax group has said it does not condone destroying the signs.
Chairman Warren Djanogly said: "None of our lot are vandalising the signs. But the council are simply going to waste more money having a dedicated team to monitor the situation.
"If I was a resident I'd be absolutely furious."