AN astonishing letter from the ABC proves it knowingly left out critical information when suggesting the Northern Territory government tortured children in detention.

The letter, from Four Corners reporter Caro Meldrum-Hanna, shows the ABC misled a key interviewee about what it planned to report and praised prison reforms it then didn’t mention on air.

The letter also confirms Prime Minister Malcolm Turnbull was a fool to let the Four Corners report panic him into calling a royal commission only 10 hours later.

Here is clear evidence that the ABC is out of control, demonstrating a bias that — with Turnbull’s naive help — will now destroy the NT Country Liberal Party government.

Three weeks ago Four Corners screened a highly emotional report claiming juveniles in detention in the NT were being abused.

This report, a month before the NT elections, opened with a shot of a young man being shackled by guards to a chair and with what seemed a bag over his head.

Host Sarah Ferguson then made clear that this was torture of the kind infamously demonstrated at Iraq’s Abu Ghraib jail: “The image you have just seen isn’t from Guantánamo Bay or Abu Ghraib but Australia in 2015 …

“This is juvenile justice in the Northern Territory, a system that punishes troubled children instead of rehabilitating them.”

I’ve written before that much of what you were told was false or outrageously one-sided.

The ABC failed to tell viewers that the young man being strapped down, Dylan Voller, was not being tortured but restrained after threatening to hurt himself.

The ABC failed to tell viewers the hood was actually a mesh to stop him spitting on guards, as he’d done hundreds of times.

And the ABC failed to give a true picture of Voller’s background. It glossed over the threat he posed, claiming: “Voller has been in and out of juvenile detention since he was 11 years old for car theft, robberies and, more recently, assault.”

False. The ABC failed to tell viewers that Voller’s first convictions for assault actually dated back seven years and that of his more than 50 convictions, 23 were for assault or other attempts to hurt people, often police and warders.

There was much more the ABC also did not tell. It had shown another confronting scene of Voller being wrestled to a mattress by guards, but did not tell viewers that one guard had been charged with using undue force and been twice cleared, once the courts was told the context.

Nor did the ABC tell viewers that this incident — presented as an attack, of a kind still continuing — actually occurred six years ago, under a Labor government.

Crucially, as former Victorian Premier Jeff Kennett detailed yesterday, the ABC also did not tell viewers that the current CLP Government had recently spent more than $20 million on reforming juvenile detention and had appointed a new Corrections Commissioner to oversee the changes.

Instead, Four Corners presented the CLP Government as torturers and its Attorney-General and then Corrections Minister, John Elferink, as a Harley-riding cowboy blind to the abuse under his nose.

But now comes Meldrum-Hanna’s letter — and now we know brazenly the ABC worked to make this report so savagely one-sided.

Meldrum-Hanna, who did that Four Corners report, on June 2 wrote to Elferink pleading for him to show her the juvenile detention centre.

That letter, obtained by my Sky News colleague Matt Cunningham, shows — in my opinion — that Elferink, was tricked by the ABC.

Meldrum-Hanna actually told Elferink what her later report never said — that “based on our research, the NT government is proactively trying to make things better for juveniles in detention”.

The letter lists many reforming initiatives — again, not mentioned in the later Four Corners report — including “Sentenced to a Job, in-prison education programs, reducing reoffending rates, restraining the growth of prisoners … barbecues being planned in Don Dale to teach the juveniles about cooking ... child protection reviews … and a new Corrections Commissioner appointed”.

It also acknowledged that the detained juveniles had been moved out of the old prison later shown in the most damning Four Corners footage.

Gushed Meldrum-Hanna to Elferink, who had overseen these reforms: “Minister Elferink, this is a significant legacy. It is also your legacy.”

So the ABC knew. It knew huge reforms had been made to juvenile justice, yet the program that Turnbull and hundreds of thousands of Australians watched suggested the exact opposite.

Take this exchange from the program:

Meldrum-Hanna: As early as 2012 … the government knew of excessive force, inappropriate solitary confinement of children in detention?

Dr Howard Bath (former NT Children’s Commissioner): Yes.

Meldrum-Hanna: And nothing was done?

Bath: As far as I know nothing was done.

Then this:

Meldrum-Hanna: The mistreatment of children has continued.

This is simply astonishing.

In a telephone conversation she actually taped before the filming, Meldrum-Hanna also repeatedly assured Elferink he would not be burned and that he could trust her to tell his story.

She even boasted to Elferink in her letter that “we (at the ABC) are not interested in ‘gotcha moments’.”

Yet Elferink claims (although Four Corners denies) the ABC even asked him to ride his Harley Davidson motorbike to the jail. That footage was then used at length to make Elferink seem a lair more interested in his bike than his duties.

On it went. In her letter, Meldrum-Hanna asked Elferink to let the ABC into the detention centre because “closing the doors on us means we cannot … give a voice to the dedicated officers and staff in Corrections who work very hard”.

Yet all that Four Corners showed of these “dedicated officers and staff in Corrections who work very hard” was footage wildly out of context of some acting violently.

And this:

Meldrum-Hanna:Four Corners has learnt the children were being cared for (in the Behavioural Management Unit) by a core group of prison officers, highly trained in professional fighting.

Seriously? That’s it? Juvenile centre works are all thugs or highly trained in “professional fighting”?

Four Corners denies any bias. Executive producer Sally Neighbour has said claims that the story was timed to cause political damage were “false, outrageous and desperate” and Meldrum-Hanna told ABC radio Elferink was given a fair hearing.

I don’t buy it. The ABC has shown outrageous bias and in doing so will have almost certainly helped to destroy another conservative government — the CLP Government, now facing heavy defeat at next week’s NT election.

It will also have smeared a reforming minister, John Elferink, who has since faced death threats and has had to leave his home.

And, of course, it conned the Prime Minister, who must now have proved to his colleagues that he trusts the ABC too readily for the Liberals’ own good — and for Australia’s.