A second monumental data blunder in the space of just four months has seen Islington Council publish personal information, including the sexuality, of almost 2,500 residents online.

While responding to a Freedom or Information (FOI) request on the website What Do They Know?, town hall officers managed to leak the names, address, relationship status, gender, ethnicity, religion and sexual preference of around 2,400 people who have been re-housed by the council.

The dossier of highly private information was freely accessible to the public for a full 19 days and exposes those involved to the risk of identity theft – although the council believes the data was only accessed seven times.

The gaffe came to light on July 16 – just four days after a briefing about the last council data leak, in which the names and addresses of 51 residents were given to suspected drug dealers on the Andover Estate in Holloway.

At that meeting, finance chief Cllr Richard Greening said: “We will more or less guarantee this won’t ever be repeated.”

One resident, who has been the victim of both data leaks, said: “I am so angry I can’t even speak. I got the letter on Wednesday and I was shocked. How could this happen again? I am very fearful now, but I don’t want to have to move.”

Cllr Terry Stacey, leader of Islington’s Lib Dem opposition, said: “This comes less than a week after we were reassured by the Labour leadership after supposedly thorough audits of data protection at the council that everything was OK and this couldn’t happen again. How wrong it seems they were.

“This is yet another data disaster, and this time more than 2,000 resident’s details are out in the public domain because of incompetence from this Labour council.”

The council says all the personal information has been removed from the site and Sean McLaughlin, Islington Council’s corporate director of housing and adult social services, has written to apologise to everyone affected by the mistake.

Cllr James Murray, Islington Council’s executive member for housing and development said: “This should never have happened. I am angry and disappointed. Islington residents need to know that their personal information is safe with the council.

“An investigation is underway and I have made clear that I want any and every lesson to be learned.”

An Islington Council spokesman said it has launched an immediate investigation and hasinformed The Information Commissioner – who is currently looking into April’s data breach.

She added: “We’re already working to improve the protection of information within the council and we will now be intensifying our efforts to ensure all staff receive appropriate training.”