Boris Johnson has been lambasted after documents obtained by the Bureau of Investigative Journalism revealed the Brazilian government had personally thanked him for refusing to support action over the Amazon fires.

As the rainforest burned last summer – fuelled by a sharp rise in deforestation that critics blame partly on Bolsonaro’s agenda – Johnson criticised a threat by President Macron of France to block the EU’s Mercosur trade deal with Brazil.

Speaking in Biarritz before the G7 summit in August, Johnson described the fires as a “tragedy” but called Macron's threat an excuse to interfere with free trade. Leo Varadkar, the Irish prime minister, had already given his support to Macron’s proposal.

Days after the G7, the Brazilian ambassador “thanked the prime minister for his stance at Biarritz, and said it had not gone unnoticed in Brasilia”, according to Foreign Office internal documents released to the Bureau through a freedom of information request.

Ed Davey, acting leader of the Liberal Democrats, said he was astounded at the revelation, especially as the UK is due to host the COP26 global climate negotiations later this year. “Any remaining credibility Boris Johnson has on climate is now gone,” he said.