Hundreds of climate activists have marched in south-western France carrying portraits of President Emmanuel Macron that they had illegally removed from town halls and which police had been seeking to recover amid a judicial crackdown.

As the G7 leaders met in Biarritz, demonstrators from a nationwide civil disobedience movement demanding more action on the climate emergency appeared in nearby Bayonne brandishing dozens of portraits the state accuses them of stealing from civic buildings.

Demonstrators said they wanted to highlight what they called the gap between the president’s official pledge to combat global heating and insufficient government action to lower emissions.

As part of the “Take down Macron” movement that began in February, non-violent protesters seized official framed portraits of Macron from more than 100 town halls stretching from small Beaujolais villages to towns in Normandy. It has led to a police crackdown and a number of trials for “group theft by deceit” will take place this autumn.

In Bayonne, a spokeswoman for ANV-Cop 21, a group promoting non-violent action in support of the Paris climate accord, said protesters had gathered with the portraits “because we want to denounce the vast gulf between Emmanuel Macon’s international decisions on the climate and his concrete action in France. While Emmanuel Macron surfs internationally on a false image of climate champion, citizens in his own country are taking him down.”

Some chanted “One, two, three degrees, it’s a crime against humanity!” as they marched through the narrow streets of Bayonne, near the French resort of Biarritz where police had sealed off the town centre for the G7 summit.

“We are holding Macron upside down to show the lack of sense in his policies,” said one demonstrator as some portraits were turned on their head.

The portraits are some of the reported 128 obtained by activists from alternative and ecological movements from French town halls since February. Photograph: Georges Gobet/AFP/Getty Images

Macron has put the climate emergency on the agenda for the G7 talks with a session on the environment and biodiversity on Monday morning. He has said he will push for concerted action to limit carbon emissions in the fashion industry, lower shipping emissions and act on the potent greenhouse gases, hydrofluorocarbons (HFCs) used in cooling units such as fridges and air-conditioners.

In a video recorded shortly before the summit, Macron said the youth climate protests had made him harden his climate stance. “I’ve profoundly changed,” he told Konbini News.

The centrist Macron styles himself as a vocal champion of fighting global heating and the guarantor of the UN’s 2015 Paris climate accord. He has challenged the US president, Donald Trump, on the issue, vowing France would “make our planet great again”. But at home, there is a “gap between ambition and reality”, the nation’s independent advisory council on the climate recently warned. France is failing to reduce greenhouse gas emissions fast enough, particularly on road transport and buildings, and is unlikely to meet its goals.

When the G7 summit opened on Saturday, more than 9,000 protesters joined a peaceful anti-G7 march across a bridge linking France and Spain. But later in the day, police used teargas and water cannon to break up protests in Bayonne, where hundreds of demonstrators chanting anti-capitalist slogans were blocked from reaching the city centre.

By Saturday evening, 68 people had been arrested, 38 of whom were taken into custody, authorities said.

Anti-capitalist activists, environmentalists and other anti-globalisation groups have converged on a G7 counter-summit in nearby Hendaye, close to the Spanish border, which has largely been peaceful.

Biarritz is a popular surfing destination that would normally be enjoying a summer tourism boom, but with Trump, Boris Johnson and other world leaders arriving for three days of talks, the resort has been in lockdown.

France deployed more than 13,000 police officers and gendarmes to secure the event amid fears of disturbances by radical anti-capitalist groups, anarchists or French “gilets jaunes” (yellow vest) anti-government protesters.