Emmanuel Macron has asked for world powers to help Brazil and its neighbours fight the fires raging in the Amazon and to plan huge replanting programmes. The appeal came as the French president piled pressure on Brazil’s far-right leader Jair Bolsonaro, who has been accused of fuelling the burning of the rainforest.

As environmental protesters marched nearby, the G7 summit’s, opening meeting was dominated by the spectre of economic repercussions for Brazil and its South American neighbours and showed how the Amazon is becoming a battleground between Bolsonaro and the west. Many governments have become alarmed that vast swathes of the Amazon are going up in smoke, affecting biodiversity and worsening the climate crisis.

Macron wants to bring other leaders onside to his hard line with Bolsonaro. The Brazilian president suggested, after talking to Donald Trump on Friday, that some countries would press Brazil’s case at the G7 in the face of criticism from France.

Paris and Dublin have threatened to block the Mercosur free-trade agreement between the EU and South American nations if Brazil does not act to slow the deforestation of the Amazon. In Biarritz, EU council president Donald Tusk increased that pressure yesterday. He said that although the EU stands by the free-trade agreement with South American nations, “it is hard to imagine a harmonious process of ratification by the European countries as long as the Brazilian government allows for the destruction of the green lungs of planet earth”.

Boris Johnson said the UK was ready to help extinguish the fires. Photograph: Andrew Parsons/PA

UK prime minister Boris Johnson underlined his concern as he arrived in Biarritz but he said he would not let it affect trade ties with Brazil. “I am horrified by what is happening in the Amazon basin, and as I said yesterday the UK stands ready to help in any way that we can to extinguish the fires, and to protect habitat and biodiversity,” said Johnson. However, he said he would not be willing to follow the example of France and Ireland in refusing to ratify the EU’s trade deal with Mercosur.

“I think I would be reluctant to do anything at this very difficult time for global free trade, to cancel another trade deal,” Johnson said.

Asked whether Macron was making a mistake linking the deal to the environment, he added: “I think we need to look at the commercial thinking that may underlie that.”

UK trade minister Conor Burns, a longtime ally of Johnson’s, toured Brazil on a trade mission this week, leading the Labour party to accuse the UK government of “cosying up” to the Bolsanaro regime.