Islington Council breach left drug-takers with residents' details
A data breach led to people reported for anti-social behaviour and drug taking getting information on those who complained.
Extra police patrols are now in place at the Andover Estate in Holloway, north London, following the breach by Islington Council.
Names and phone numbers of 51 complainants were passed to 10 people facing a ban from the estate.
The council has apologised to the affected residents.
A group of people, who are not from estate, began gathering there earlier this year and residents complained about loud music, smoking drugs and verbal abuse.
The council had prepared legal injunctions against 13 people to ban them from the area, and 10 had been served this month.
But those 10 were also given paperwork including a log of all calls reporting anti-social behaviour, with names, phone numbers and street or estate names if they were given.
Louise Round, Islington Council's corporate director of resources, said: "This information should not have been released, and we are extremely sorry that, through an error on our part, it has been disclosed.
"The council is in the process of contacting every single person who is on that list - in total 51 people - to offer our apology and any practical support we can give.
"This includes additional security measures if they request it.
"We're working closely with the police, who are putting extra patrols on the estate to reassure residents and deter any further anti-social behaviour."
She added the breach has been reported to the Information Commissioner and a review of procedures is taking place to help prevent such an incident again.