Research by the Centre for Ecology and Hydrology found that species of wild bee exposed to oilseed rape crops treated with neonicotinoids suffered declines between 2002 and 2011.
Worst impacted was the lime-loving furrow bee, which lost 23% of its population; Hawthorn mining bee populations fell by 18%.
The average bee population decline was 7% from 2002-11, when neonicotinoids came into wide-scale commercial use in England. The pesticide is under an EU-wide two-year ban amid concerns over its impact on bees, such as damaging ability to forage and navigate, and their colony growth.
The research looked at changes in occurrence of 62 species with oilseed rape cropping patterns across England between 1994 and 2011, examining data from 31,818 surveys across 4,000sq km of land.
Nick Isaac, co-author of the paper, said: “The negative effects that have been reported previously, they do scale up. They scale up to long-term, large-scale, multi-species impacts that are harmful.”
Friends of the Earth’s nature campaigner Paul de Zylva has urged the UK government to continue the pesticide ban after Britain leaves the EU.
He said: “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 how we test and license pesticides for use.”
The National Farmers’ Union (NFU) said the research does not show the chemicals cause widespread decline in populations.
NFU bee health specialist 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 neo- nicotinoids are causing widespread declines in pollinator populations and it certainly does not show that neonicotinoid use has caused any extinction of bees in England.”
Dr Hartfield, who said farmers are well aware of the importance of bees and would not want to cause them harm, called for more science-based regulation but warned against over-regulation of chemicals for fear of the effect on the farming industry’s future.
“Without many of these [plant protection] products, our ability to produce wholesome, affordable food for the nation will continue to stagnate”, he said, adding there are knowledge gaps and a “limited evidence base” to guide and inform policymakers on the issue.
The report’s authors said neonicotinoids must be seen as a contributory factor to decline in bee populations, citing a “complex array of drivers” including habitat, climate change and disease were also important.
“It’s likely that there’s a whole series of interacting factors and while people like a one-shot solution, it’s probably not the case in most situations,” he said.