A senior United Nations official has slammed the Australian government over the offshore detention of asylum seekers, saying he’s concerned about the “shocking” mental health situation of detainees on Nauru.

Indrika Ratwatte, the Asia and Pacific director for United Nations High Commissioner for Refugees (UNHCR), said on Tuesday the issue of the refugees on Nauru should be prioritised, describing the mental health of the asylum seekers he saw as “very, very shocking.”

“We must make every effort to get refugees out of this situation.”

Mr Ratwatte made the comments in Canberra after returning from an inspection of Australia’s offshore processing facilities on Nauru, where more than 1200 asylum seekers have been languishing since 2014.

He said 40 children had spent their entire lives in detention on Nauru and another 60 had spent half their lives there.

Mr Ratwatte said the growing trend to self-harm, and children as young as 10 attempting suicide, is “symptomatic of the despair and hopelessness that is prevailing there”.

“Nobody should be in a position to seek such dire recourse.”

He cited the fear of family separation as a major mental health issue, giving as an example a 14-year-old girl said to be in a catatonic state on Nauru after being separated from her mother who was taken for medical treatment is in Australia.

“These situations need to be avoided,” he said.

He has also urged Australia to rethink its offshore detention policy.

“While there is a perspective that this is a policy that takes people away from harm and death at sea, we should make sure that approach does not lead to individuals eventually being harmed on land.”