A UK-based campaign to pressure Barclays to stop its multibillion pound funding of fossil fuel corporations is spreading to countries around the world.

In the civil disobedience protests, organised by the grassroots Labour group Momentum and activists from People and Planet, campaigners disrupted business at 40 Barclays branches across the UK in March.

Now it has organised the next round of peaceful protests at more than 60 branches of the bank – including sites in Germany, the US and Canada.

The campaign is backed by the shadow chancellor, John McDonnell, who last week joined a conference call of more than 200 organisers from 10 different countries.

John McDonnell: ‘Climate breakdown is the fault of bankers who plough billions of dollars into the fossil fuel companies.’ Photograph: Mark Thomas/Rex/Shutterstock

McDonnell described the protests as a “vital, urgent initiative”, adding that he would encourage all Labour members to join.

“Climate breakdown isn’t caused by ordinary people,” he said. “It’s the fault of bankers who plough billions of dollars into the fossil fuel companies. Governments cannot stand by while the finance sector profits from destroying the planet while we’re left with environmental catastrophe and extortionate energy bills.”

The campaign comes amid signs of growing environmental activism among grassroots Labour supporters. Last week, Momentum protesters joined Extinction Rebellion activists outside parliament in Westminster to back Jeremy Corbyn’s call for it to declare a climate emergency.

A separate grassroots group – Labour for a Green New Deal - is rallying support for the party to adopt a radical green agenda at constituency parties across the country ahead of the Labour conference in the sutumn.

A Momentum source said: “It feels like climate is going to be the issue for Labour activists over the next year. There is definitely a growing consensus that only a radical transformation of the economy and society will cut it, with many activists taking inspiration from Alexandria Ocasio-Cortez’s Green New Deal in the US.”

Organisers say the Barclays campaign has been inspired by the school climate strikes, in which 1.4 million young people took to the streets earlier this year to voice their fears about the escalating ecological crisis, and the Extinction Rebellion protests last month in London, during which more than 1,000 people were arrested.

The “UK Uncut-style” protests aim to put pressure on Barclays, which organisers say is one of the leading European backers of fossil fuel projects, financing 15 fossil fuel companies with more than $30bn (£22.6bn) from 2012-17, including corporations pushing plans to develop the fracking industry in the UK.

A recent report from the Rainforest Action Network and the BankTrack group, which tracks and analyses the investments of banks around the world, found Barclays was “the top European banker of fracking and coal [and] leads as the worst European bank, with $85bn poured into fossil fuels and $24bn into expansion”.

In response, Barclays has highlighted investments made by the bank in environmental schemes and stated that in 2018 it had “facilitated” £27.3bn in “environmental and social financing”.

A spokesperson added: “Our approach balances the need to accelerate the transition away from the most carbon intensive fossil fuel sources, with ongoing financial support for clients operating responsibly in energy sectors that are expected to contribute significantly to the world’s energy mix.”

In the next round of Momentum’s campaign, on 25 May, thousands of people will join pickets and occupations at more than 60 Barclays branches across the world. Actions are planned in Germany, Holland, the US, Canada and the UK, with organisers from Mauritius, Romania and Shanghai signed up to organise future actions.

Activists say they plan to “creatively disrupt” the running of Barclays branches by turning them into children’s play areas and pop-up discos, adding they will talk to customers about the banks’ “funding of climate change” as well as handing out chocolates to staff to apologise for the inconvenience.

McDonnell said although Labour would implement a “radical programme to tackle climate change and transform the economy with a green industrial revolution” it would need support from grassroots campaigns.

“Policy proposals from the top down aren’t enough,” he said. “In order to win, we need to build a movement of working-class people who can take on the banks and force them to stop funding climate change.”

Natasha Josette, a member of Momentum’s national coordinating group, said: “Climate change is devastating communities around the world and the banks who fund fossil fuel infrastructure are to blame … Only the banks have the money to fund these big fossil fuel infrastructure projects, and are a key link in polluting the planet and causing climate breakdown.”