Islington Council in north London published details of the sexual orientation of over two thousand tenants after an error with a Freedom of Information request last month.

For nearly three weeks, the names, addresses, relationship status, gender, ethnicity, and religion details of 2,376 residents was available online through the Freedom of Information request website WhatDoTheyKnow.com.

On 26 June, the housing department responded to a request that had been filed through the website, where responses to queries are automatically published, about ethnicity and gender of people who had applied for council housing.

But the spreadsheets it sent back included names, marital statuses and addresses of nearly 2,400 residents, along with their stated sexual orientation. Some personal information was visible, some was in ‘hidden sheets’ in the emailed attachments.

MySociety.org, which created the FOI request website, reports on the accidental leak that while some of the personal data was not immediately visible, anyone with basic knowledge of spreadsheet software could uncover it.

MySociety.org said the spreadsheets did not attract much public attention before a volunteer noticed them and acted to have them removed three weeks after their publication online.

It notes that someone had tried to use the ‘recall’ function on Microsoft Outlook email system to retrieve the original email, without success.

The council said an investigation has now been launched. The Information Commissioner’s Office was informed by MySociety.org.

Liberal Democrat leader Terry Stacy told the Islington Tribune the council was “incompetent” as it followed a leak in which 51 names and addresses of people who had lodged complaints about anti-social behaviour were reportedly made available to those behind it.

At the time of that leak, Labour councillor Richard Greening had said: “We will more or less guarantee this won’t ever be repeated.”