Mental health probe after NSW boy's death

The NSW premier has vowed no stone will be left unturned in an investigation into the mental health system after a Sydney father accused of stabbing his son to death was denied care weeks before the incident.

The 36-year-old man allegedly stabbed his five-year-old son in his bed at their Carlingford home in the city's northwest on Friday morning.

The boy's mother, a nurse, told The Daily Telegraph she had previously begged health authorities for help for her "sick" husband, who cannot be named for legal reasons.

The Northern and Western Sydney Local Health Districts said on Tuesday there would be a full investigation into the ongoing care and treatment of the man.

The investigation, to be carried out by NSW Health chief psychiatrist Dr Murray Wright, will examine the man's ongoing care, including the period leading up to the boy's death.

Premier Gladys Berejiklian said "no stone will be left unturned" in the investigation.

Labor leader Luke Foley said there were major issues in the state's health system and the government owed it to the young boy to investigate and make improvements.

The father has been charged with murder.

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