Mia Mottley made the comments at the Cop27 climate summit in Egypt, where world leaders and campaigners are gathering to discuss action to meet global targets.
The prime minister said it was important to understand “why we are not moving any further” on tackling the climate crisis.
“I don’t need to repeat the horror and devastation over the course of the last 12 months since we met in Glasgow,” she said in a speech to the summit.
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“The simple political will that is necessary - not just to come here and make promises but to deliver on them and to make a definable difference on the lives of the people who we have a responsibility to serve - seems still not to be capable of being produced.”
Ms Mottley called for a massive overhaul of international development loans and a 10 per cent tax on fossil fuel companies.
“We need to have a different approach, to allow grant-funded reconstruction grants going forward, in those countries that suffer from disaster,” she said at an event hosted by Nicola Sturgeon at the conference.
“Unless that happens, we are going to see an increase in climate refugees. We know that by 2050, the world’s 21 million climate refugees today will become 1 billion.”
This made reference to a previous study that looked at how many people could be forced to leave their homes in the next 30 years as extreme weather events become more frequent and more intense due to global warming.
The UN Refugee Agency says the climate crisis tends to first create internal displacement before cross-border migration.
Ahead of this year’s conference, known as Cop27, leaders and experts have been ringing alarm bells that time is fast running out to avert catastrophic rises in temperature.
For the first time, delegates are to discuss demands by developing nations that the richest, most polluting countries pay compensation for damage wreaked on them by the climate crisis - which is called “loss and damage” in climate negotiations.
Rishi Sunak, the UK prime minister, dealt a blow to vulnerable countries by ignoring pleas for climate reparations in his speech to the conference.
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