Future UN climate summits should be held only in countries that can show clear support for climate action and have stricter rules on fossil fuel lobbying, according to a group of influential climate policy experts.

The group includes former UN secretary-general Ban Ki-moon, the former president of Ireland Mary Robinson, the former UN climate chief Christiana Figueres and the prominent climate scientist Johan Rockström.

They have written to the UN demanding the current complex process of annual “conferences of the parties” under the UN framework convention on climate change – the Paris agreement’s parent treaty – be streamlined, and meetings held more frequently, with more of a voice given to developing countries.

“It is now clear that the Cop is no longer fit for purpose. We need a shift from negotiation to implementation,” they wrote.