The Susi Air pilot was taken hostage by the Liberation Army fighters on February 7 shortly after landing on a remote Paro airstrip in Nduga, Highland Papua.
In recent months, Hipkins has been reluctant to comment on the situation, saying it was not appropriate to discuss details publicly in case it compromised Mehrtens’ safety.
However, while at a press conference in Auckland today, Hipkins read a statement urging Mehrtens’ captors to release him immediately.
"There’s absolutely no justification for holding hostages," Hipkins said.
"The longer he is held the harder this becomes for him and his family.
"I’ve been kept closely informed on developments for the last six months. Our efforts remain on resolving this safely."
Hipkins said Mehrtens’ whānau was being supported by the Ministry of Foreign Affairs in New Zealand and in Indonesia.
"I acknowledge this is an incredibly challenging time for them."
The Kiwi appeared in a video in April flanked by his separatist rebel captors calling on Indonesia to stop air strikes in Nduga. He said the actions were unnecessary and put his life and lives of other innocent people at risk.
The father-of-one was carrying five passengers, including a baby, from Mozes Kilangin Airport in Mimika, in Central Papua, to Paro Airport in Nduga.
Susi Air founder and former Minister of Maritime Affairs and Fisheries of Indonesia Susi Pudjiastuti told the Herald Mehrtens was one of the airline’s best pilots.
A friend and former colleague had described Mehrtens as a "quiet and serious" man who was originally from Christchurch.
Mehrtens is married to a woman of Indonesian descent and had been living in her home country for quite some time. He speaks fluent Bahasa, the main language spoken in Indonesia.
Conflicts between indigenous Papuans and Indonesian security forces are common in the impoverished Papua region, a former Dutch colony in the western part of New Guinea that is ethnically and culturally distinct from much of Indonesia. Papua was incorporated into Indonesia in 1969 after a UN-sponsored ballot that was widely seen as a sham. Since then, a low-level insurgency has simmered in the mineral-rich region, which is divided into the Papua and West Papua provinces.
