A fatal oxygen mix-up at a western Sydney hospital which killed one baby and seriously injured another was caused by the incorrect installation of gas pipelines, flawed testing and governance failures, a report has found.

A baby boy died and a newborn girl suffered suspected brain damage after they were mistakenly given nitrous oxide or “laughing gas” instead of oxygen at Bankstown-Lidcombe Hospital in June and July this year.

A final report released on Saturday by NSW Chief Health Officer Dr Kerry Chant found “a series of tragic errors” led to the incidents.

Dr Chant said she hoped the report gave the families of the two babies some answers.

“I can imagine that whilst giving some of the answers the families must require, it still doesn’t undo what’s been done, the catastrophic impact this error has had,” Dr Chant told reporters in Sydney on Saturday.

“We’ve certainly let them down and we should have done better.”

The family of the dead baby boy criticised NSW Health Minister Jillian Skinner for not giving them enough time to consider either the interim or final reports before releasing them publicly.

Dr Chant would not say why Ms Skinner decided not to attend the press conference.

Opposition Leader Luke Foley said it was a disgraceful “dereliction of duty” that no government ministers fronted the public about the report.

“It’s utterly outrageous that when two babies are gassed nobody from the cabinet of NSW can be bothered to front up and speak with the public about it,” Mr Foley told reporters outside the hospital.

A report has found staff at Sydney’s south-west hospital failed in their responsibilities. Photo: Facebook

He said Ms Skinner should immediately stand down or be sacked, and an independent external investigation into the deadly bungle be launched.

In a brief written statement, Ms Skinner said the public could be assured the health system was safe.

“The Ministry of Health will accept all recommendations raised in the Chief Health Officer’s final report to ensure this tragic error can never happen again,” she said.

The report found that both South West Sydney Local Health District and BOC Ltd, who installed the medical gas piping, failed to comply with Australian standards.

It also unearthed broader clinical and governance issues around risk management, communication and lines of accountability.

Investigation continues

The general manager of the hospital has been suspended following investigations, after an engineer at the hospital was suspended earlier this month.

Further interviews of senior managers are now taking place in relation to the investigation.

Dr Chant would not say whether they would face the sack, saying they deserved procedural fairness while the probe was underway.

The South Western Sydney Local Health District will also be placed on “performance watch”, while most contracts with BOC Ltd have been severed.

NSW Health will now require that different contractors carry out the installation and testing of gas pipelines.

Medical gas outlets in all other NSW health facilities have since been tested and no other failures found.

A coroner will investigate the circumstances surrounding the baby boy’s death.