The group, which includes some of the world's smallest and poorest countries, is a counterpoint to the G20 group of leading industrialised and emerging economies.
It pointedly held its inaugural meeting just ahead of a gathering of G20 finance ministers in the Peruvian capital Lima, where economic policy-makers from around the world are gathered this week for the annual meetings of the International Monetary Fund and World Bank.
"We are low- and middle-income, least developed, arid, isthmus, landlocked, mountainous and small island developing countries," the group said in statement.
The group, which aims to both raise and manage climate funds, agreed to set up a public-private "climate risk pooling mechanism," a sort of insurance fund for extreme weather events and disasters.
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The launch came as the clock ticks down to key United Nations climate talks in December that will seek a comprehensive deal on curbing carbon emissions and saving the planet from the potentially disastrous impacts of global warming.
Funding for poor and vulnerable nations has been a major sticking point in previous climate talks.
The V20's inaugural chair, Philippine Finance Minister Cesar Purisima, said the cost of falling short would be astronomical.
"In the absence of an effective global response, annual economic losses due to climate change are projected to exceed USD 400 billion by 2030 for the V20," he said.
UN climate chief Christiana Figueres urged "ambitious and timely finance" to help the V20 countries.
"Climate change is not only an environmental issue, it is a fundamental economic issue and needs financial solutions," she said.