A royal commissioner has asked the Northern Territory Government to explain the leak to a journalist of a document from former child detainee Dylan Voller that reportedly shows a list of people he once wanted to kill.

At a directions hearing this morning at the Royal Commission into the Protection and Detention of Children in the Northern Territory, co-commissioner Margaret White said the leak was "disturbing".

She asked the NT Government solicitor-general Sonia Brownhill to provide an explanation for how a document, which had been provided to the royal commission, was leaked to the media.

Commissioner Margarete White wants to find out who leaked the document. ( ABC News: Xavier La Canna )

The document, first published by Sky News yesterday, reportedly shows a list Dylan Voller wrote while in detention of people he wanted dead and how he wanted to kill them.

"It's a document that on its face would be in the possession of the Northern Territory Government in some form or another," Ms White said.

"It is said in the report that I read, that it was a document before the commission and the Northern Territory Government is the conduit through whom all those documents come to the commission."

'We want to get to the bottom of who leaked document'

Ms White asked Ms Brownhill to begin her enquiries with the NT Department of Corrections and report back during scheduled hearings in Alice Springs next week.

An image of Dylan Voller strapped to a chair with his head covered aired on Four Corners. ( Supplied )

"We would like to get to the bottom of who has provided the news agencies with the document," Ms White said.

"It appears to be in breach of all the undertakings that have been given by the parties with respect to documents."

Ms Brownhill agreed to investigate, but told the hearing the NT Government had provided the document to the royal commission and therefore was not the only body that had it.

"As you are directing me to seek an explanation from the Department of Corrections, I will endeavour to do so," Ms Brownhill said.

NT Government unsure how investigation will progress

Speaking at a press conference this afternoon, the NT Attorney-General Natasha Fyles said the Government was still working out what form the investigation would take and whether police should be involved.

Voller's treatment in youth detention featured heavily in the Four Corners program that sparked the royal commission.

The program aired leaked footage of Voller's treatment, including images of him held in a restraint chair with his head covered in a spit hood.

He was the first former juvenile detainee to give formal evidence at the inquiry last year.

Voller 'extremely disturbed' by leak

Today his lawyer, Peter O'Brien told the commission, Voller was "extremely disturbed" by the leak and called for the royal commission to hold its own "independent" inquiry into the leak.

"It [the leak] has tremendous potential to not only prejudice him and besmirch his character in these proceedings but also jeopardises his chances of rehabilitation," Mr O'Brien said.

The Darwin Press Club said use of surveillance to try to uncover a journalist's sources would always be a concern.

Press Club concerned about electronic surveillance

Helen Davidson, Darwin Press Club vice president, said some incredibly important stories had only come to light because of whistle-blowers.

"But part of that is that people need to be protected, and the onus of protection falls on the journalist," she said.

"That is something we abide by as part of a code of ethics.

"And if government or authorities are going around that and using electronic surveillance techniques to find out our sources, I think that's a really, really concerning state."

The ABC has contacted Sky News for a comment.