The United Nations has accused the Turnbull government of making an empty promise to settle refugees in Australia if they had family ties here.

Publicly, the government has always vowed that no refugee on Manus Island or Nauru would ever be settled in Australia.

But the UN High Commissioner for Refugees said it agreed to oversee the resettlement deal with the United States on the “clear understanding” some could move to Australia.

“Last November, UNHCR exceptionally agreed to help with the relocation of refugees to the United States following a bilateral agreement between Australia and the US,” commissioner Filippo Grandi said on Monday.

“We agreed to do so on the clear understanding that vulnerable refugees with close family ties in Australia would ultimately be allowed to settle there.

“UNHCR has recently been informed by Australia that it refuses to accept even these refugees, and that they, along with the others on Nauru and Papua New Guinea, have been informed that their only option is to remain where they are or to be transferred to Cambodia or to the United States.”

A spokesperson for Immigration Minister Peter Dutton stood by the government’s position.

“The position of the Coalition government has been clear and consistent,” the spokesperson told The New Daily on Monday.

Mr Grandi said refugees would suffer further if they remained separated from family members.

“This means, for example, that some with serious medical conditions, or who have undergone traumatic experiences, including sexual violence, cannot receive the support of their close family members residing in Australia,” he said in a statement.

“There is no doubt these vulnerable people, already subject to four years of punishing conditions, should be reunited with their families in Australia. This is the humane and reasonable thing to do.”

Mr Grandi said the UNHCR had no choice but to continue its endorsement of the resettlement deal with the US to avoid “prolonging” refugee suffering.

The Asylum Seeker Resource Centre (ASRC) accused the government of misleading the UN and called on the government to reunite families.

“Parents we work with have missed out on important milestones in their children’s lives.Young people are desperately worried about elderly parents they have been prevented from caring for,” ASRC detention advocate Natasha Blucher said.

“Those on Manus Island and Nauru simply want to be united with their families in safety.

“The only thing stopping these families from being together is the government’s choice.”

The government and Labor opposition both argued offshore processing was required to stop people smuggling and deaths at sea.

Mr Grandis said the “dire humanitarian situation” of offshore processing was not the solution.

“There is a fundamental contradiction in saving people at sea, only to mistreat and neglect them on land,” he said.

“I urge Australia to bring an immediate end to the harmful practice of offshore processing, offer solutions to its victims, for whom it retains full responsibility, and work with us on future alternatives that save lives at sea and provide protection to people in need.”

Of the 2000 people in offshore detention, 1100 remain on Nauru and 900 remain on Manus Island after four years in operation.

More than 1100 refugees have been referred to the US for resettlement over the past eight months. Another 500 people are waiting for the outcome of the refugee status determination.

The Turnbull government brokered the relocation deal with former US president Barack Obama. There were fears President Donald Trump may not honour the deal, however he has recommitted to it.

The US has committed to settling hundreds of legitimate refugees. It’s not yet clear where the remaining refugees will be settled.

The New Daily has contacted the UNHCR for further comment. A spokesperson for Mr Turnbull declined to comment.

-with AAP