Activists marched through the town of Bayonne, close to where G7 leaders are meeting in Biarritz, carrying portraits of French President Emmanuel Macron stolen from town halls across France.
Climate campaigners wanted to highlight what they say is the gap between the French president's promises on tackling climate change and the policy of his government.
The protest is the culmination of a months-long civil disobedience movement, part of which has seen activists remove official portraits of Macron from city council buildings.
The activists took 128 officials portraits of Macron prior to the protest, and fifty-seven of the climate activists will have to appear in court over the stolen portraits, the group said.
"This is an empty portrait that symbolises the emptiness of Emmanuel Macron's policies," said Gaël, a climate activist who marched in Bayonne. "He's not respecting his commitments in favour of the environment and it's time to start."
Another climate protester, Esther, said politicians often made lofty promises for goals they hope to achieve by 2050.
"But we must act now," she said.
The climate activists said 900 people joined the protest, which was unauthorised.
A heavy police presence prevented others from taking to the streets.
Aurélie Trouvé, the spokeswoman for the Alternatives G7 group that held counter-protests to the G7 summit said they were cancelling a planned protest near Biarritz after one of the people key to the mobilisation was arrested.
"We don't think that it is reasonable to continue on with this protest action under these conditions. And we deplore this police state that is preventing us from carrying this political message, but we want to continue on with it, so we're only postponing this action," Trouvé said.
Tourists visiting the region also remarked on the heavy police presence in the area.
Watch Euronews correspondent Guillaume Petit report on the protests in the player above.