Victoria's embattled child protection department has again been caught leaking private information – even after an internal inquiry identified a litany of breaches.

Three months after the Andrews government pledged better training for staff, the Department of Health and Human Services released a file containing protected information about dozens of children in foster care.

This breach, out of a government office that has already come under scrutiny for failing to safeguard confidential information, occurred while the agency is under investigation by the state's privacy commissioner.

A department caseworker sent a spreadsheet to a Melbourne foster carer showing details of multiple expenses that had been claimed for children in out-of-home care. It identified more than 30 vulnerable children.

The document names all the children, some who are siblings, and has an itemised description of the claims, which include DNA testing, psychological assessments and medical appointments.

It also lists their Client Relationship Information System numbers, the workers involved in the case and the names of the organisations providing services, such as child care agencies.

A basic internet search of the children's names returns information about their primary schools, sports clubs and extracurricular activities.

"I was horrified," the foster carer said on Tuesday. "It's just complete stupidity. I couldn't believe they just sent me all this information. It's quite private and I'm quite sure that the families and the children wouldn't want other people knowing this stuff."

The alarming revelation comes just days before the Commissioner for Privacy and Data Protection is expected to hand down his report into the scale of earlier breaches from the leak-plagued agency.

Fairfax Media last year revealed DHHS has been breaching the privacy of children and foster carers for more than a decade, and paying them off or upgrading home security if they find out about it.

They include instances where workers mistakenly gave confidential Children's Court documents and internal department files to parents who posed an ongoing threat to their children.

In one of a series of privacy breaches that were uncovered, social workers handed a father who was jailed for vicious attacks on his sons the protected address of where his other children were living in foster care.

Some breaches resulted in break-ins, threats and menacing phone calls, and, in at least three confirmed cases, the agency paid to install security systems at foster carers' homes.

In July last year, Families and Children Minister Jenny Mikakos ordered an internal review of the child protection system to identify whether there were systemic problems with its handling of confidential information.

Released in September, the review found the agency's breaches put traumatised children and carers "at direct risk of harm" at least 58 times in the past five years.

The report, which traced breaches to every DHHS division in Victoria, said the real number of families put at risk was likely to be higher. "In a small number of instances there was a risk of severe and potentially catastrophic impact, e.g. serious injury of a carer or child," reviewer John Leatherland wrote.

In the worst cases a foster parent was assaulted, primary school children were relocated, and a carer's car was doused in petrol. In all but one breach that was examined, human error was blamed.

At the time, Ms Mikakos said the safety of carers and children was paramount and the department pledged to implement all the recommendations from the report, which centred around staff training and improving internal systems.

But sources say this latest privacy breach shows the problems have not been addressed and stem from social workers being overworked.

A DHHS spokesman said it was developing a new information system to track and report privacy breaches.

"Any claim of a privacy breach is taken very seriously," he said. "In response to a recent independent review, we're developing a training strategy for all employees to meet the specific needs of child protection, housing workers and others."

Privacy and Data Protection Commissioner David Watts launched an investigation into the department six months ago and is expected to release his findings in the coming days.