The Centre for Ecology and Hydrology (CEH) which conducted the study published in Nature Communications, said that the results show that use of neonicotinoid pesticides "is a contributory factor leading to wild bee species population decline" and that their use on oil-seed rape crops is a "principle mechanism of neonicotinoid exposure among wild bee communities".
It added that neonicotinoid-treated oil-seed rape is a "principle mechanism of neonicotinoid exposure among wild bee communities" and for some vulnerable species of wild bees, the use of neonicotinoid pesticides on crops "was equivalent to at least 20 per cent of local population extinctions".
The NFU have campaigned for exemptions for neonicotinoids to be used on oil seed rape.
NFU bee health specialist Dr Chris Hartfield said: "This study is another interesting piece to an unsolved puzzle about how neonicotinoid seed treatments affect bees. It does not show that neonicotinoids are causing widespread declines in pollinator populations and it certainly does not show that neonicotinoid use has caused any extinction of bees in England.
"What we must remember here that bees provide valued agricultural pollination which is essential in food production. Farmers have increased their planting of pollen and nectar mix – food for bees – by 134 per cent in the past two years. Over 7,000 acres of seed mixes for bees have been voluntarily planted by farmers to enhance land lying fallow. It is not in any farmers’ interests to harm bees.
"In addition, oilseed rape in particular is a crop that provides a rich source of food for bees early in their foraging year. Unfortunately it’s a source of food for the pest Cabbage Stem Flea Beetle as well which is known to wipe out swathes of the crop. This pest is the reason why insecticide seed treatments are essential in growing a healthy harvest of oilseed rape. While thousands of farmers are working towards more integrated ways of managing pests, plant protection products remain an essential part of the toolbox for farmers.
"While this study claims to provide an important contribution to the evidence base underpinning the current EU moratorium on some uses of neonicotinoids, experts reviewing all the evidence have concluded that there are still major gaps in our knowledge and a limited evidence base to guide policymakers.
"The NFU remains committed to its lobbying for science-based regulation across the board and this very much includes the regulation which is restricting farmers’ use on plant protection products. Without many of these products, our ability to produce wholesome, affordable food for the nation, will continue to stagnate."
Friends of the Earth’s nature campaigner Paul de Zylva said: "This is the strongest ever evidence of harm to bees from neonicotinoid pesticides in British fields.
"The study uses data from real field conditions over 17 years and adds a huge new peak to the existing mountain of evidence showing the risk these chemicals pose to our bees.
"If the government genuinely wants to safeguard Britain’s bees, it must keep the ban on neonicotinoid pesticides regardless of what happens with Brexit - and tighten the way pesticides are tested and licensed for use."
Describing the impact of neonicotinoid pesticides on wild pollinators as "horrifying", Soil Assocition head of policy for farming & land use Emma Hockridge said the results "add to the strong and quickly growing body of overwhelming scientific evidence which points to the damaging impact of neonicotinoid pesticides on pollinating insects".
But industry body the Crop Protection Association said: "As the authors note, the decline of wild bee populations is known to be linked to a range of issues including habitat loss, climate change, intensive farming and the impact of the Varroa destructor mite – all of which have intensified during the 18 years covered by the data.
"There is still no evidence to suggest that restricting neonicotinoids helps bee populations, but it certainly harms farming and food production."
The Centre for Ecology and Hydrology (CEH) which conducted the study said that the results show that:
• Use of neonicotinoid pesticides "is a contributory factor leading to wild bee species population decline" and that their use on oil-seed rape crops is a "principle mechanism of neonicotinoid exposure among wild bee communities";
• Neonicotinoid-treated oil-seed rape is a "principle mechanism of neonicotinoid exposure among wild bee communities" and for some vulnerable species of wild bees, the use of neonicotinoid pesticides on crops "was equivalent to at least 20 per cent of local population extinctions…";
• "…neonicotinoid use is correlated with wild bee biodiversity losses at a national scale and has implications for the conservation of bee communities in intensively farmed landscapes"; and
• The benefit to bees of feeding on oil-seed rape is "more than nullified by the effect of neonicotinoid seed treatment on a range of wild bee species" and bee decline is "on average, three times stronger" in bee species that regularly feed on treated oil-seed rape than in species that feed on a wider range of flowering plants.