Activists from the Extinction Rebellion group have targeted a British Sugar factory in Norfolk.
The demonstrators accuse the company of heading in the "wrong direction" on climate change.
They staged their protest at its plant in Wissington, south west Norfolk, which is the largest sugar refinery in Europe.
The group claims British Sugar is among the largest emitters of CO2 in the county and accused it of supporting the use of a controversial pesticide.
The company insists, however, that it is "playing its part" in reducing emissions, with a target to cut its CO2 by 30pc by 2030.
The protest was organised by members of the King's Lynn and West Norfolk branch of Extinction Rebellion.
A spokesperson said: "Despite being banned across Europe, British Sugar has repeatedly and successfully sought permission from the government to use the insecticide thiamethoxam, a 'neonicotinoid', which is known to harm bee populations.
"At a time when nature is under great pressure, particularly vital pollinators like bees, British Sugar is putting profits ahead of planet by using neonicotinoids.
"Also British Sugar’s Wissington site is the largest emitter of CO2, the greenhouse gas most responsible for global heating, in our borough of West Norfolk."
On its website, British Sugar said it is focused on reducing its environmental impact "across every aspect of our business."
It adds: "For British Sugar, sustainability is economic, social and environmental. These three pillars set out the areas where our knowledge and resources are enabling us to make a positive change."
In 2021, British Sugar got permission to use a neonicotinoid to help combat a disease harming the beet crop.
It said at the time: “Supporting bee populations is extremely important to us and our growers and having the right controls to ensure this was key to the application. The treatment is applied to the seed before it is sown – it is not a spray."
British Sugar has been contacted for comment.
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