Pacific states have been urged to ensure migrants can access basic healthcare and essential income support amid the Covid-19 pandemic.
The UN Human Rights Office (OHCHR) and the International Organization for Migration (IOM) say the situation of temporary seasonal workers is concerning.
In a statement, the UN agency said migrant workers risked slipping into situations of irregularity if they could not or did not wish to return to their home countries.
It said border closures, restrictions on departure and re-entry, expired working visas and loss of employment for many temporary visa holders across the Pacific had left many of them with limited access to alternative livelihood options, adequate food and shelter.
It said these also had implications on the workers' physical and mental health.
The OHCHR said an estimated 330,000 Pacific-born people resided overseas with 2.7 million more temporary visa holders living in Australia and New Zealand.
Thomas Hunecke, the head of OHCHR in the Pacific, said his office continued to track human rights issues across the region.
Mr Hunecke said human rights-based responses to the health crisis were vital in ensuring all "migrants, regardless of their status, have access to basic social security such as healthcare and essential income support".
He said these should be an integral element of the pandemic response in the Pacific.
"In particular, we are concerned that the lack of inclusive income security measures means that many migrants and their families with little reserves would be hardest hit by unemployment and rising prices.
Meawhile, the IOM Pacific Coordinator Pär Liljert said migrants had played a vital role in supporting countries during the Covid-19 crisis and that safe migration should be part of the recovery process.
Mr Liljert said this could be a potential solution for Pacific countries that received significant GDP contributions from remittances, but equally for countries of destination by filling critical labour market gaps including in essential services like food production.
"At the heart of addressing Covid-19 and building back better are policies and programmes that guarantee the health and safety of migrants, with inclusive public health responses and socioeconomic recovery packages."
Mr Hunecke said as the long process of protecting and rebuilding economies adversely affected by the pandemic got underway, there was a need for Pacific states to ensure their response effectively addressed the disproportionate impact the crisis had on people and communities who were already marginalized and vulnerable.