Travellers have pitched up at Cannon Hill Common for the third time in less than four weeks.
A convoy of caravans and vans first arrived at the common on Monday, September 3, and have repeatedly returned - between setting up illegal camps at Mostyn Gardens, Kenley Road car park and on land near Links Avenue, Morden.
The group was moved on from each site by Merton Council and police, but returned to Cannon Hill Common earlier this week.
Debbie Shears, Conservative group leader and councillor for Cannon Hill ward, , blamed their return on the Council's failure to act and on a lack of preventative measures.
She said: "We are furious they have come back.
"I contacted the chief executive [Ged Curran] to ask for his intervention because we are getting nowhere.
"I’m having emails flooding in and residents are furious.
"Ward councillors now feel absolutely let down because of the inaction of the council.
"I can’t say it any stronger than that - it’s just inaction by this council."
She suggested installing a "natural barrier" to prevent further illegal camps and said logs could be repositioned to prevent vehicles gaining access to the common.
Coun Shears said: "We don’t want to put up a fence of anything - it’s an open common - but it needs to be protected.
"Dog owners are feeling threatened; parents are not going over there as much as they were."
Merton Council confirmed they were aware of the travellers’ return and were working to resolve the issue.
Councillor Andrew judge, cabinet member for environmental sustainability and regeneration, said: "We have informed the travellers that they will have to move on from the common and are working to ensure the site is vacated as soon as possible.
"To address the challenge of securing open land, we are looking at ways in which we can deter such illegal encampments on Canon Hill Common in the future."