Syngenta said that a European Food Safety Authority (EFSA) report on the risks posed to bees was "fundamentally flawed".
The European Commission — the Brussels-based executive of the 27-nation European Union — aims to rein in the use of such pesticides in a bid to prevent a disastrous collapse in population of an insect considered vital to the food chain.
"The European Commission has been using this flawed EFSA report to justify proposed restrictions on this technology," Syngenta's chief operating officer, John Atkin, said in a statement.
Last month, the EFSA said that neonicotinoid insecticides used in maize, rapeseed, sunflower and cotton cultivation posed "disturbing" risks to with bees and other pollinating insects hugely important for food production, especially of fruit.
EFSA said the insecticides attack the central nervous system of insects, causing paralysis and death.
The chemicals in doubt — clothianidin, imidacloprid and thiamethoxam — are present in insecticides produced by Syngenta and German counterpart Bayer.
According to Syngenta, however, further review has shown that the EFSA based its assessment on "unrealistic and excessive" seed planting rates, between two and four times higher than would be used in modern agriculture.
Syngenta — the top player on the global agrichemical market — said that using normal sowing rates in the study would have told a different story.
It claimed that the EFSA would have concluded that the risk to bees is extremely low and that in reality neonicotinoid technology is safe.
Earlier this month, Atkin told AFP that Syngenta would do all it could to defend the reputation of its products.