United Nations representatives have joined the criticism of the Abbott government's boat tow-back policy and called on Australia to process asylum seekers who reach Australian waters instead of returning them to Indonesia.

But Immigration Minister Scott Morrison has refused to change tack, saying he "completely disagrees" because the “policy is working”.

The regional head of the United Nations High Commission for Refugees also revealed that Australia has refused to provide information to its inquiry about three asylum seekers who claim they had their hands deliberately burned during a tow-back mission in January.

And UNHCR senior regional protection adviser Tom Vargas criticised Australia’s proposal to send refugees to Cambodia, saying it was “not in the spirit of resettlement”.

The frank broad critique come after a two-day conference in Jakarta, attended by Australia’s deputy ambassador to Indonesia David Engel and representatives of 14 other countries, to discuss the protection of refugees in the region.

UNHCR regional coordinator James Lynch said that with millions of people displaced around the world, solutions engineered by single countries alone would only work temporarily.

Mr Lynch said he understood the Australian government was worried about loss of life at sea, criminality in the people smuggling trade and economic migration dressed up as asylum seeking.

However, he said Australia’s policy of sending boat arrivals to Papua New Guinea or Nauru, and of returning boats to Indonesia even if people had entered Australian water or landed on Australian territory (as happened in a number of recent tow-backs) are against the refugee convention.

“If someone arrived in Australian waters, we’d expect as a requirement of the refugee convention that they be allowed to disembark and have access to asylum procedures … We’d expect [Australia] to honour their obligations,” Mr Lynch said.

Mr Vargas said: “If every state in the region decides they’ll close the door, then there will be nowhere safe for people to go.”

But the Immigration Minister was unmoved.

"I completely disagree," Scott Morrison told Sky News on Wednesday morning. "I'm not surprised, they have always opposed our turn-back policy.

"But I'll tell what Australia's national shame was when it comes to this issue, almost 1200 people dead," he said. "That's national shame. That's the regional shame."

Mr Lynch conceded that there had been no increase in asylum seeker numbers seen in either Thailand or Malaysia as a result of Operation Sovereign Borders.

The Jakarta office of the UNHCR has previously said the number of new people registering with them has dropped from 100 per day to 100 per week since Operation Sovereign Borders began.

Only 2 per cent of applicants now fail to appear for a second appointment — down from 50 per cent last year, when many were getting on boats rather than waiting for resettlement through the UN.

Mr Lynch said his organisation had written to Australia seeking information about allegations dating from January that three asylum seekers on board a wooden boat being turned back had their hands deliberately burned by sailors working for Operation Sovereign Borders.

The response from Australia had been: “We don’t need to do an investigation because we’ve done nothing wrong,” Mr Lynch said.

The UN is also yet to receive requested information from Australia about its proposal, outlined in February, to resettle refugees in Cambodia.

“From our point of view, resettlement is looking for durable solutions for refugees … who have had to flee their homes,” Mr Vargas said.

“A real solution is not to send them to a country that is still recovering from a horrible civil war that killed millions of its people … It’s not in the spirit of resettlement as far as I can tell”.

Opposition immigration spokesman Richard Marles said unilateralism was not meant to be a "long term sustainable answer in the flow of people coming by boat to Australia".

"We are worried about what this means in the context of our relationship with Indonesia in circumstances where they do not agree with this policy," Mr Marles said.

A spokesperson for Mr Morrison said on Tuesday that “the test of effectiveness for any policy, and for ongoing support of the Australian government, is whether that policy is working.

“After four months without a single successful people smuggling venture to Australia, and even longer since anyone has perished at sea on such ventures, the Coalition's strong border protection policies are clearly working … It is also pleasing to see that the inflow to Indonesia and the flow through from Malaysia has also been reduced, demonstrating that the Australian Government's strong stand is also benefiting the region.

“Australia will continue to employ the policies that have been so effective under Operation Sovereign Borders. Any venture seeking to enter Australia illegally will be met with the same measures that have prevented other such attempts to date.”

The conference was opened on Monday by the Indonesian foreign minister, Marty Natalegawa, who launched a veiled attack on Australian policy, saying the region should be looking at “shared responsibility" for the irregular movement of people, "not shifting responsibility”.

The rebuke from the UN has followed the publication of explosive footage by Fairfax Media showing Manus Island security guards attacking asylum seekers 24 hours before Iranian Reza Barati was killed.

Mr Morrison said the footage should be turned over to the independent investigation led by retired public servant chief Robert Cornall.

"I would say to anyone who has information of that nature: that's the place for it to be investigated," Mr Morrison said. "I want to get to the bottom of this. I want to make sure I know exactly what has happened."

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