A group of former leaders and climate experts said the annual U.N. COP climate talks were no longer fit for purpose and needed to be reformed, publishing a critical open letter mid-way through what has so far been a fractious summit.

The United Nations' COP climate talks are "no longer fit for purpose" and need an urgent overhaul, key experts including a former UN secretary general and former UN climate chief have said. In a letter to the UN, senior figures say countries should not host the talks if they don’t support the phase out of fossil energy.

Leaders on a panel with members of the High Ambition Coalition, a group of nations that want to see strong climate action, highlighted the “inverted morality” of big emitters who aren’t taking responsibility for their impacts on countries who have the most to lose.