The UN fund to help developing countries fight climate change can be spent on coal-fired power plants – the most polluting form of electricity generation – under rules agreed at a board meeting.

The green climate fund (GCF) refused an explicit ban on fossil fuel projects at the contentious meeting in Songdo, South Korea, last week.

"It's like a torture convention that doesn't forbid torture," said Karen Orenstein, a campaigner for Friends of the Earth US who was at the meeting. "Honestly it should be a no-brainer at this point."

The fund was set up as part of the ongoing UN climate negotiations to help developing countries finance clean energy and measures to help adapt to climate change.