A baby boy, covered in blood, has been pronounced dead on arrival at a Darwin hospital amid mounting concerns the child protection system in the Northern Territory is in crisis.

Five cases of suspected child abuse have emerged in as many days, with the NT's Child Protection Minister Malarndirri McCarthy admitting funds are only just touching the surface of the problem.

"You are dealing with a lot of children in the Northern Territory," the Labor MP told reporters in Darwin on Tuesday.

"They are incredibly tragic, some of them are stories that can really turn you up inside."

Police are investigating the death of a six-week-old boy, rushed by ambulance to Royal Darwin Hospital about 4.45am (CST) on Tuesday.

He was pronounced dead on arrival in the emergency department.

Sources told the ABC the child had been bashed and was covered in blood, and that his family was known to child protection services.

Ms McCarthy refused to talk about the details of the case, saying it was now a matter for police and the coroner.

She also declined to comment on the four other cases in the public spotlight.

In each of them, the Department of Health and Families is suspected of failing to formally investigate warnings of children at risk.

"The time for evasion and denial is over," opposition MP Jodeen Carney told AAP.

"The public have the right to know why the minister's department failed to act on highly credible warnings of potential child abuse.

"It is clear that the child protection system is failing children in the Territory."

Parliament was told last Friday about a baby who suffered broken limbs and bleeding on the brain after his mother died of swine flu.

He had been placed in his uncle's care despite the "serious concerns" of child protection workers.

The department opted not to investigate the notifications, and the child was found "wheezing and largely unresponsive" less than a month later.

He's currently in an Adelaide hospital with suspected permanent brain damage.

On Tuesday it emerged that senior paediatrician Paul Bauert wrote a letter to the Department of Health and Families in July.

He outlined the case of a boy who had repeatedly returned to hospital with severe malnutrition, saying the child would be at "extreme risk" if he was returned to his parents, and that "failure to act promptly on this ... may result in this child dying".

But when health staff followed up on the concerns 10 days later, they were told child protection workers would not conduct a formal investigation.

"I am deeply concerned if there are many letters going off by medical professionals," said Ms McCarthy, who admitted that the first time she had heard about the case was on morning radio.

"If those concerns are not listened to of course I need to ask questions as to why that is happening."

Ms McCarthy said Labor had committed "extraordinary resources" towards child protection in the NT.

"But we also recognise that it's not a fail safe system," she said, as she denied additional funds were being spent in the wrong places.

"It's a sign that the need is great, it's a sign that the issues surrounding our children across the Northern Territory, we are just touching the beginning of."

In the other two cases, documents sighted by the ABC indicated the department didn't want to know about the drug history of a woman whose newborn baby went into opiate withdrawal, while another baby was discharged from hospital with its homeless mother.

Child protection workers were aware of the case before the woman left but had failed to act in time.

Ms McCarthy conceded there were obviously "unhappy and frustrated" people within the health system who had leaked the cases to the media.