Addressing the SNP conference, Susan Aitken claimed that the Prime Minister is only interested in environmental projects to use for "a wacky photo op".
The SNP councillor said she believed the Conservative minister responsible for Cop26, Alok Sharma, was working hard to secure an agreement to tackle the climate emergency at next month's conference in Glasgow but was being hindered by Mr Johnson.
Ms Aitken said: "Cop26 President Alok Sharma is, I believe, doing his level best to secure a Glasgow agreement worthy of the name, but he's undermined at every turn by his party leader who's only really interested in green infrastructure as something to stick a union flag on and pose beside for a wacky photo op.
"But Glasgow, Scotland and the SNP can lead the way, and Cop26 can give us a pivotal moment to do so.
"We know what the prize is: clean air, local food security, an end to fuel poverty, better, cheaper public transport, green spaces for all and sustainable high-value skills and jobs in a resilient modern economy."
Bemoaning the absence of the Scottish Government from conference negotiations, Ms Aitken said: "We still have an incredible opportunity to put Glasgow and Scotland in the global front window for sustainability, to showcase not only our climate ambition but also our practical plans to lead the world and delivering a just transition to zero-carbon economy and society.
"Scotland's climate action, ambitions and policy agenda, our growing international reputation for business and technological innovation, the challenges from our past that we're overcoming, our incredible wealth of natural assets, I don't think any other region on Earth has such a platform to showcase ourselves and our ambitions, this year, as Scotland does."
The council leader said an early estimate of the cost to decarbonise Glasgow was £30 billion but said: "We in the SAP also need to be clear that this is not only necessary, it's worth it.
"Not only because if we don't respond to the climate emergency now, the cost later, and not just the financial cost, will be so much higher."