Convicted murderer Scott Watson had made little progress in identifying appropriate treatment arising from risk factors identified four years ago, the Parole Board says.
Watson was serving a life sentence for the killing of Olivia Hope and Ben Smart on New Year's Day in 1998.
His latest bid for parole was declined earlier this month.
Watson, who continued to profess his innocence, has now appeared before the board three times.
The Parole Board said in a written decision that Watson, now 49, had behaved well in prison and Corrections was positive about his work and behaviour, but little progress had been made since matters raised in 2016.
At that stage, a postponement order was made for a period of four years, and the board said he needed intensive treatment because he was "very high risk".
Watson's parole request included that he had a suitable address, and good oversight with family and friends. His partner of 16 years appeared at the 3 December parole hearing, and was noted as being supportive, as were his family and friends.
He also had possible employment, either with a carving institute or doing renovations.
His lawyer submitted that his risk could be managed in the community with tight conditions.
The board said Watson remained an "undue risk" and could not be released.
"First, referring to our decision of 2016, we identified in that decision his risk factors. We then invited those risk factors to be taken and for Corrections to consider what appropriate treatment might be provided to Mr Watson."
The board said that took into account Watson's denial of the index offending, but that was "not seen as an insurmountable problem".
"Unfortunately, Mr Watson has not been able, over an extended period, with the help of psychologists to identify his treatment needs and start treatment."
Corrections believed it had provided Watson with reasonable opportunities to identify and begin the appropriate treatment.
"Mr Watson feels that they have not been prepared to help him and have insisted that he confess to the crime or have placed other impediments in his way," board chair Sir Ron Young said in the written decision.
He said it was not for the board to try to resolve these issues.
"Recently, Mr Watson has been offered the opportunity of having further sessions to identify treatment needs. He has agreed to do so, but only on the basis that he could audio record those sessions.
Psychological services were not prepared to agree to this, but were happy for Watson to have a support person, and for that person to take notes.
Watson has since agreed to drop his insistence for the sessions to be recorded, and was commended for his willingness to compromise, which Sir Ron said indicated a "clear way forward".
The board said Watson's appeal before the Court of Appeal should not be an impediment to Corrections being able to identify treatment needs, and to begin that treatment.
The board indicated it planned to see Watson again by the end of November 2021, but for the reasons given, considering that he remained an undue risk.