Papua New Guinea has placed last of the Pacific counties on Transparency International's 2008 Corruption Perceptions Index, or CPI.
The yearly list measures the perceived levels of public-sector corruption in a given country and draws on different expert and business surveys
On a scale from one to ten, Papua New Guinea scored two, placing it 151st equal over all.
Tonga, which has stated its commitment to move towards a democratically elected government by 2010, saw its CPI score rise to 2.4 in 2008, from 1.7 in 2007, coming in at 138 equal.
Solomon Islands, with a CPI score of 2.9, was placed 109th, equal with Vanuatu, and Kiribati ranked 96th in the world.
Australia scored 8.7, coming in 9th on the list overall, while New Zealand shared first equal with Denmark and Sweden, on a score of 9.3.
Huguette Labelle, the chair of Transparency International, says in the poorest countries, corruption levels can mean the difference between life and death, when money for hospitals or clean water is in play.
She says the continuing high levels of corruption and poverty plaguing many of the world's societies amount to an ongoing humanitarian disaster.