Leading scientists and environmentalists called on Boris Johnson and Emmanuel Macron to declare an immediate ceasefire in a bitter Anglo-French row over fishing rights on Saturday as fears grew that the UK’s arguments with its EU neighbours could overshadow the crucial Cop26 summit on climate change.

On the eve of the UK hosting 120 world leaders at the meeting in Glasgow, the prime minister said the summit would be “the world’s moment of truth” and could mark “the beginning of the end of climate change”. Speaking at a meeting of G20 leaders in Rome, he added: “The question everyone is asking is whether we seize this moment or let it slip away.”

But as the countdown continued, there was exasperation among green groups and scientists at the way UK and French governments were at each other’s throats in an argument over fishing rights, at a time when the UK is also threatening to invoke article 16 of the Northern Ireland protocol in a move that could trigger a new trade war with the EU.