Parliamentarians from 20 Asian and Pacific nations have declared the climate crisis a critical threat to human health in the region.

A forum on global health hosted by Fiji's Parliament last week made the statement as part of the 'Nadi Communique'.

Fiji's Speaker, Ratu Epeli Nailatikau, chaired the meeting and said climate change was one of the greatest threats to health with immense implications for societies and economies.

Increasingly frequent and severe weather events mean there are more injuries and deaths, higher rates of infectious and mosquito-borne diseases, as well as food and nutrition insecurity, Ratu Epeli said.

The climate crisis is also a threat to safe drinking water, housing, and employment opportunities and has an impact people's mental health, he said.

The Western Pacific regional director for the World Health Organisation, Takeshi Kasai, stressed the need for widespread climate action policies.

"Climate change is not just a scientific argument, it is a real threat to people," Dr Kasai said.

The issues are complex but time is running out to take action on present and future health threats, he said.

Dr Kasai called for politicians to drive positive policy change because "without health, we have nothing", he said.

The 5th Asia-Pacific Parliamentarian Forum on Global Health included lawmakers from Cambodia, Cook Islands, Fiji, Federated States of Micronesia, Japan, Kiribati, Laos, Malaysia, New Zealand, Niue, Palau, Philippines, Republic of Korea, Samoa, Solomon Islands, Thailand, Tonga, Tuvalu, Vanuatu and Viet Nam.

The forum said it noted "with alarm" that global warming of 1.5 degrees celsius was expected to threaten the very existence of low-lying island nations because of sea-level rise and climate-related disasters.