Victoria's coroner will not release an official report into the death of murdered schoolboy, Luke Batty, amid fears it would undermine the state's child protection service.

The 11-year-old was killed by his father Greg Anderson, at Tyabb cricket ground, south-east of Melbourne, in February.

At the time of his death there were several intervention orders and outstanding arrest warrants against Anderson, who died after being shot by police at the scene.

A child protection case on Luke had been closed.

The Commissioner for Children and Young People, Bernie Geary, conducted an inquiry into the case but the coroners court was told in August his report would not be ready in time to be included in the inquest.

Luke's mother, Rosie Batty, told reporters outside the court that the news was a huge disappointment.

She also queried the worth of Mr Geary's role.

Ms Batty's reaction lead to Mr Geary publicly declaring the report would be ready, as promised.

But lawyers acting on the commission's behalf sought to stop it being released publicly on the grounds it would be contrary to public interest.

The application to suppress the information was backed by the Department of Human Services (DHS), responsible for the child protection sector.

Report's release could hinder future inquiries: coroner

Acting on behalf of the DHS, barrister Erin Gardner told the inquest there would be "a lack of desire on behalf of child protection workers to take part in an open and honest way" in future inquiries if their identities were revealed, and the information was going to become public.

A teary Rosie Batty lashed out at Bearnie Geary in August over the timeline for his report. ( AAP: Julian Smith )

"They might say I wish I hadn't participated in that process because I was cross-examined," Ms Gardner said.

"Word would spread in the workforce... where anything you do or say could be used against you."

Ms Gardiner said the report was "irrelevant" and using it would jeopardise the inquiry process, and the ongoing work of Mr Geary and the commission.

"The status quo ought to remain," Ms Gardner said.

"The report ought not to be used or circulated or published in any way... in the interest of public health and safety in this state."

But Rachel Doyle SC, acting on behalf of Luke's mother, said the department's argument assumed child protection workers would put their "self-interest and fear" above the public interest.

"It's a very dim and cynical view of the professionalism of child protection workers," she said.

"There is no need for Your Honour to take such a cynical view.

"It also flies in the face of witnesses that have trooped through the witness box and shown such anxiety, and a willingness to see improvements."

Secrecy will reduce public confidence in system: media lawyer

Media lawyer Justin Quill also urged the coroner to release the information in light of "an overarching public interest in the judicial system being open, for the purpose of public confidence".

"Where there is secrecy, there is real potential to undermine public confidence in those services," he said.

"If there's secrecy around this report... people will be less understanding, less confident in the system."

Mr Quill said participants in inquiries should not assume material would be confidential, or not be disclosed on the public interest.

He said "speculation" they might be less inclined to cooperate was unjustified.

Coroner Gray acknowledged there were "clearly, strongly competing public interest" in the issues raised.

But he said "protecting the integrity" of the Commission for Children and Young People "outweighs public disclosure of the report".

Coroner Gray said he did not accept the report was irrelevant for his purposes and would include it in his own assessment of the case.