A letter has since been sent by retailer The Cooperative and supported by Pesticide Action Network (PAN) UK to new Defra secretary Owen Paterson calling for an "urgent independent review of the science and regulatory assessment" of the pesticides.
PAN UK director Dr Keith Tyrell said: "It is clear that the concerns of NGOs and the public are now being echoed by the retailers. The weight of evidence is growing and it is time for clarity."
But Syngenta's head of product safety Dr Phil Botham said in a letter to The Independent: "Often the link between pesticides and declines in bee health is presented as a given. This ignores declines in bee health in places where pesticides are not used and that neonicotinoid-based seed treatments have been used safely across millions of hectares of European crops for 10 years.
"The sustainability of business and agriculture depends on the sustainability of pollinators. We should all focus on finding real solutions to this serious problem."
A report in June by the European Food Safety Agency questioned whether results from three recent scientific studies could be compared with "realistic field conditions". It is due to publish its own study of the effects of five neonicotinoids on bees in December.