“Australia cannot walk away from its responsibility to guarantee the safety of these men who have already suffered so much uncertainty and fear,” said Mr McMillan.
Water and electricity were turned off on Tuesday and food and medical services are no longer being provided. The men are surviving on stockpiles of food and water collected from rain.
The Australian Government plans to transfer the refugees to other accommodation closer to the island's main town of Lorengau.
However, the refugees are refusing to leave with some of the men repairing wire security fences to the compound to protect themselves inside the centre.
The UNHCR has also expressed its concerns about the lack of planning in the closure of the facilities and insufficient consultation with the Papua New Guinean community.
There remains no long-term solution for the refugees on Manus Island who are not included in the relocation arrangement with the United States of America.
“It is clear the refugees inside the Manus Island processing centre hold grave fears for their safety and security in the other locations,” said Mr McMillan.
“The Government must take immediate steps to ensure the refugees remain safe and continue to have access to water, food and critical medical and mental health services,” said Mr McMillan.
The Uniting Church has long advocated for refugees to be processed fairly, onshore in Australia and for an increase in Australia’s humanitarian intake.
“We pray for the safety of these men as the centre is shut down today and all refugees who continue to be deprived of hope.”