Mick Gooda and Margaret White have been appointed as co-commissioners into the inquiry into the Northern Territory’s youth detention system, following the resignation of former chief justice Brian Martin just four days after he was appointed.

Mr Gooda is the Aboriginal and Torres Strait Islander Social Justice Commissioner with the Human Rights Commission, and is joined by Ms White, a former Queensland Supreme Court Justice.

Attorney-General George Brandis said Mr Gooda had the respect of both sides of politics and was an obvious candidate for the role.

"Mr Gooda's name was prominent among those recommended," he said.

"We've heard and heeded the many indigenous voices who have asked for the representation of an Indigenous person on the royal commission."

Brian Martin, Mick Gooda and Margaret White. (AAP)

Ms White served for more than two decades on the Supreme Court of Queensland and Senator Brandis said she was well known, highly regarded and eminently well qualified to conduct the royal commission.

Neither commissioner comes from the NT.

Following accusations of a conflict of interest over his daughter's employment as an adviser to the former NT attorney-general, Mr Martin said today he would step away from the proposed seven-month inquiry.

Questions were also raised whether Mr Martin had a personal conflict, given he may have sentenced young people involved in the inquiry who were potentially abused behind bars.

Mr Martin said his decision to resign was solely his own.

"My resignation does not imply any criticism of the government, prime minister or the attorney-general," he told reporters in Canberra.

He said it became apparent, "rightly or wrongly", he would not have the full confidence of sections of the indigenous community that have a vital interest in the inquiry.

"As a consequence, the effectiveness of the commission is likely to be compromised from the outset. I am not prepared to proceed in the face of that risk. This royal commission is far too important to undertake that risk," he said.

Brian Martin with Malcolm Turnbull at last Thursdays's announcement. (AAP)

Mr Martin dismissed suggestions that he would have ignored or not given sufficient weight to indigenous issues.

"This suggestion is wrong," he said, adding that he had been making plans to consult widely with indigenous organisations and individuals.

Given the response to his appointment, Mr Martin believed there was much to be said for the suggestion the commissioner should come from outside the NT.

As well, he said, there was some advantage "both in practice and in appearance" in having an Indigenous person as commissioner.