Farmers’ leaders have expressed concerns about a report confirming the risk to bees posed by a controversial pesticide.

Neonicotinoids, used to coat oilseed rape seeds to protect the young plants from attack from a pest called cabbage stem flea beetle, have already been broadly banned in the European Union in the face of opposition from farmers’ groups.

Now the European Food Safety Authority (EFSA) has published updated assessments of three neonicotinoids – clothianidin, imidacloprid and thiamethoxam – and says “most uses” of the pesticides represent a risk to wild bees and honeybees.

The conclusions update those published in 2013, which resulted in the European Commission imposing restrictions on their use.

The new assessments, which this time cover wild bees – bumblebees and solitary bees – as well as honeybees, involved the EFSA’s Pesticides Unit carrying out an extensive data collection exercise, including a systematic literature review, to gather all the scientific evidence published since the previous evaluations.

Jose Tarazona, head of EFSA’s pesticides unit, said: “The availability of such a substantial amount of data as well as the guidance has enabled us to produce very detailed conclusions.

“There is variability in the conclusions, due to factors such as the bee species, the intended use of the pesticide and the route of exposure. Some low risks have been identified, but overall the risk to the three types of bees we have assessed is confirmed.”

But National Farmers’ Union (NFU) senior regulatory affairs adviser Dr Chris Hartfield said they were concerned that the assessments failed to take proper account of what is happening to bees in real field situations.

“Evidence shows there are a number of factors affecting them and that the greatest declines in bee biodiversity pre-date the use of neonicotinoids,” he said.

“The reality is that there is a balance between environmental protection and food production that has to be considered and the impacts of a ‘no neonicotinoid’ scenario on pollinators also need to be fully assessed.”

Matt Shardlow, chief executive at conservation group Buglife, urged the EU to ban the pesticides completely.

“It is a tragedy that our bees, moths, butterflies and flies have been hammered by these toxins for over 15 years,” he said.