The council is taking urgent steps to prevent a giant water fight being staged in Battersea Park next month.
The council has learned that people are being invited to take part in a mass water fight in July via the social networking website Facebook.
People thinking of attending are now being warned that they will not be allowed into the park and that if they breach any of the park's byelaws they will face prosecution.
The organisers are also being contacted via Facebook to be warned that they are likely to face legal action if the event takes place.
All constables in the parks police service, including dog handlers, will be on duty on the day in question and will be supported by numerous officers from the Metropolitan Police.
Anyone caught breaching the park's byelaws faces fines of up to £200 upon conviction in a magistrates court.
The park's byelaws cover a wide range of activities and are designed to prevent nuisance in the park. There are a number of specific byelaws prohibiting the activities now being advertised online, including the use of water pistols and other similar items, fighting, brawling, using offensive language or causing annoyance to other park users.
The warning to the organisers and those thinking of taking part comes just a few days after a similar mass water fight in Hyde Park led to widespread disruption and disorder in the park and in nearby Oxford Street. A number of people were arrested for public order offences and assault and one man was arrested for committing grievous bodily harm after events spiralled out of control.
The council's environment spokesman Cllr Sarah McDermott said: "We do not intend to sit idly by and allow the park to be used for a mass water fight. We will not tolerate people coming into the park and causing distress and annoyance to families and other visitors.
"Many people may be thinking of attending because they believe it will be a harmless and amusing day in the park. Unfortunately experience elsewhere has shown that whenever these events are organised they normally descend quite rapidly into violence, mayhem and misery for the innocent people caught up in it.
"We are already liasing with the Met Police to get extra police officers into the area on the day in question, while all the resources of the parks police service will be deployed to make sure this event does not happen.
"Officers will be stationed at all the entrances to the park and they will refuse entry to anyone they believe has arrived for a water fight. If having been turned away these same people are then caught inside the park, they will be removed, as will anyone we find actually engaged in a water fight. We will then seek to prosecute all of these people in the magistrates court.
"We are also looking into the possibility of taking a number of other contingency steps on the day to physically ensure that these plans are foiled.
"My advice to anyone thinking of coming to Battersea Park for a water fight is stay away."