A concrete source of climate fund has been raised in a U.N. text for the first time, suggesting raising money by capping emissions from the shipping sector to help developing countries tackle climate change.

Tim Gore, policy advisor for Oxfam [File photo]

The text, released and implemented by the International Maritime Organization (IMO) on Tuesday in Durban, South Africa, proposes that money raised by "specific actions" to reduce emissions from maritime bunker fuels, which could be used to finance climate adaptation through a Green Climate Fund.

Tim Gore, policy advisor for Oxfam, said: "Delegates are starting to see that international shipping is the most promising new source of finance for the Green Climate Fund."

"Support for this proposal is coming from a growing number of developing and developed countries, but it will be for ministers to decide if a deal can be cut here in Durban."

The draft did not define whether revenues would be raised by a levy.

"We cannot allow the Fund to kick-off as an empty shell. It is essential that negotiators defend this text and ensure it is part of a final package at the end of the week," said Gore.

International shipping accounts for around 3.3 percent of the world's man-made carbon dioxide emissions and could grow by 150 to 250 percent by 2050 if regulation is not in place.

Last month, campaign groups Oxfam and WWF urged a carbon price of $25 per ton should be applied to shipping fuel (known as bunker fuel) to help cut emissions and generate $25 billion a year by 2020.