Breach exposed personal details including medical information and prison records.

An investigation has been launched after yet another data leak by Islington Council.

On Sunday, it emerged personal information about penalty charge notices was freely available on the council’s parking appeals website.

Information included scanned cheques, medical information to justify appeals - and even one person’s prison record.

It is the council’s third data breach in the space of four years.

In April 2012, officers inadvertently handed details of 51 Andover Estate residents in Finsbury Park to the same gang members they had ­reported to the council for terrorising their neighbourhood. Six families had to be rehoused at an estimated taxpayer cost of £50,000.

Just three months later, the authority published details – including sexuality, ethnicity, religion and mental health problems – of around 2,400 people on the What Do They Know? website in response to a Freedom of Information request.

It had to pay over £100,000 in compensation and fines for both leaks.

An investigation has now been launched into the latest breach, looking into whether the data was accessed. It has also been reported to the Information Commissioner’s Office.

The offending part of the parking appeals website was immediately taken offline when the council was notified.

A council spokesman said: “We are extremely sorry about this incident.

“We are very grateful to the responsible local residents who pointed this problem out to us so that we could take action.”

Terry Stacy, former Liberal Democrat leader of the council, was one of those who told the authority on Sunday night.

He told the Gazette: “We were assured by the Labour council that this could never happen again. How wrong it seems they were.

“This is yet another data disaster. Confidential information has ended up in the public domain because of the incompetence of the council.

“Someone’s head needs to role for this, and we should start with politicians who run the council.”

While the investigation continues, drivers appealing against penalty charge notices will temporarily be unable to access pictures of their incident online. The council apologised for the inconvenience this will cause.