Speaking at the Virtual Climate Summit on Thursday, Ralph Regenvanu said Vanuatu had benefited the least from fossil fuels, but been ravaged as a result of their emissions.
Mr Regenvanu said he was putting the fossil fuel industry and the states that sponsor it on notice.
"My government is now exploring all avenues to utilise the judicial system in various jurisdictions - including under international law - to shift the costs of climate protection back onto the fossil fuel companies, the financial institutions and the governments that actively and knowingly created this existential threat to my country."
His comments echoed an urgent recommendation to tax carbon emissions from an October United Nations climate report which predicted disastrous consequences from global warming even at 1.5 degree Celsius.
This is well below the current target of two degrees set by more than 200 countries signing the Paris Agreement in 2015.
The Marshall Islands is chairing the Climate Vulnerable Forum's 'Virtual Climate Summit.'
The Forum comprises the 48 countries most threatened by climate change.
Leaders from France, Canada, New Zealand and the Pacific are participating.