About 400 refugees are still refusing to leave the former detention centre on the Papua New Guinea island after it was closed at the end of October when essential services were cut.
The deputy regional representative of the UN refugee agency (UNHCR), Nai Jit Lam, said Australia remained responsible for the refugees and should engage them in constructive dialogue.
"This is a man-made and entirely preventable humanitarian crisis. It is a damning indictment of a policy meant to avoid Australia's international obligations," the UNHCR added.
Yesterday, PNG police said they planned to convince the men to leave the centre voluntarily, but today they said they were waiting for the outcome of court action by the refugees' lawyer in the PNG Supreme Court.
The police said there was a risk of diseases such as typhoid, dysentery and cholera in the centre, where the health of the men was now in peril, according to a team of advocates, who secretly entered the facility last week.
Mr Lam agreed the health of the men was a concern, but he said the refugees saw the standoff as an opportunity to show and tell the world about how they had been treated since being forcibly transferred to PNG in 2013.
The UNHCR said it was grateful to other states in the region "for offering assistance and real solutions for this group of traumatized and vulnerable human beings.
"Establishing interim care for these refugees and asylum-seekers, and finding lasting solutions for them outside of Papua New Guinea, are now the most critical priorities," it said.
"UNHCR urges States to continue their engagement with Australia and the PNG government and to advocate to bring an end to the human suffering."
It said Australia had exiled approximately 3000 refugees and asylum-seekers to Pacific islands, with about 1200 still in Nauru and 900 in PNG.
Despite government announces to the contrary, Mr Lam said alternative facilities being built on Manus Island were still not ready to hold the men.
"The accommodation outside of the former centre is still under construction," he said.
"We were there and saw for ourselves that they are trying to complete the site as quickly as possible. But the fact remains that major work is still in progress and might take a couple of weeks before completion."
Outside the centre, basic services needed by the refugees, such as healthcare, were also not adequately provided, according to Mr Lam.
"We observed that initially four caseworkers were planned to look after over 700 individuals' well-being. From what we have observed firsthand, none are operating as of today," he said.
"This is due to local contractual disputes among people here as well. The other concerning issues that we have observed are regarding security and the lack of interpreters on the Island, that brings about the issue of how they would communicate with local people or even the police as well."
Mr Lam said tensions with the local community remained.
"In the last three to four days, there were two incidents reported... Someone from the local village came and switched off the (Hillside Haus) generator because it was too noisy," he said.
"And there was a blockade of a road by local people at the main site of what we call West Lorengau Haus."
Mr Lam said the locals' anxiety and fear of what was happening had not been resolved.
Australian foreign minister Julie Bishop rejected the UN criticism.
"There is accomodation that is perfectly acceptable, indeed many people have moved there already, and those that have stayed on Manus Island are chosing to do so to try and force Australia to take them, " she said.
But from inside the centre, the Kurdish refugee Benham Satah said the refugees did not want to go to Australia.
"If Australian government don't want us in Australia, okay, we don't want to go there as well. Just let us go to safe country. Let us go to New Zealand, because we are not going to leave this centre unless you give us freedom," he said.
Photo: supplied. The 113th daily protest in the detention centre, 22-11-17.