Toxic pesticides blamed for harming bees are still being used across large swathes of farmland in Scotland, according to the latest government monitoring.

Farmers have treated potatoes, wheat, barley and oats on more than 22,000 hectares of land with the three most dangerous nicotine-based chemicals known as neonicotinoids.

The revelation has prompted wildlife groups to step up their campaign for Scottish ministers to ban the pesticides permanently to protect bees. But farmers say this could be “premature and damaging”.

The European Union (EU) restricted the use of three neonicotinoids in December 2013, and is now considering whether to end or extend the restrictions. They were clothianidin, imidacloprid and thiamethoxam.

But the restrictions do not prevent the three chemicals from being used on crops that don’t attract bees and other pollinators. In Scotland, this has allowed their continued use on potatoes, wheat, barley and oats.

The latest figures from the Scottish Government’s Science and Advice for Scottish Agriculture show that the three pesticides were applied to crops covering 22,442 hectares of farmland in 2014. That included 11,477 hectares of winter wheat, 5,910 hectares of winter barley, 4,379 hectares of potatoes and 676 hectares of spring oats.

Experts point out that the chemicals do not remain in the crops. “Neonicotinoids can leach into the soil and contaminate wild flowers growing in field margins, thereby impacting insects even if they are not foraging on the crop itself,” said Dr Penelope Whitehorn, an ecologist at the University of Stirling.

“There is very good, consistent evidence that neonicotinoids have serious impacts on a range of species such as bumblebees and solitary bees. These unintended impacts include a reduced ability to navigate and forage successfully and a lower breeding success,” she argued.

“The evidence is not complete, but it is certainly compelling enough to make precautions necessary to protect our native pollinators - especially given the importance of these species to the environment and the economy.”

Wildlife groups wrote to Scottish ministers in December demanding an all-out ban on the three pesticides, but have yet to receive a reply. They are hosting an open discussion entitled ‘Moving Beyond Neonicotinoids’ in the Scottish Parliament on March 1.

“The Scottish Wildlife Trust wants the Scottish Government to permanently ban the three neonicotinoids that are most harmful to bees and other wildlife from use on all crops grown in Scotland,” said the trust’s head of policy, Dr Maggie Keegan.

“The EU ban still allows these toxic chemicals to be used on crops that are not attractive to pollinators. But we now know these chemicals don’t stay put as they are taken up by wildflowers, get into watercourses and persist in soils meaning there is no escape for bees, butterflies and other wildlife,” she added.

Matt Shardlow, the chief executive of the insect conservation group Buglife, accused the UK government of failing to act on neonicotinoids. “The partial ban put in place by the EU has helped reduce the exposure of wildlife to these agrotoxins, but they are still being widely used as sprays and seed treatments for cereals,” he said.

The National Farmers Union in Scotland stressed that sound science had to be the main driver in the decision-making process. “Calls for blanket bans in the absence of scientific evidence are both premature and damaging,” said the union’s deputy director, Andrew Bauer.

“The European Union, who lead on such matters, view the use of some neonicotinoid products on certain crops as safe and their continued responsible use in Scottish agriculture is both legitimate and necessary.”

The Scottish Government’s scientific advisor, Professor Louise Heathwaite, has advised that neonicotinoids could cause “harmful sub-lethal effects to honeybees”. But she thought there was not enough evidence on whether they affected the health of honeybee colonies.

According to a government spokeswoman, Heathwaite believed that “in general land-use change and intensification, and the resulting loss of floral resources, are likely to be critical factors affecting pollinator decline.”

The spokeswoman added: “The Scottish Government supports Europe’s precautionary approach towards the use of neonicotinoids and the continuation of the current restrictions on their use.

“However, the European legislation allows the use of three neonicotinoids for example as a seed treatment on winter cereals and as sprays on potato crops…We will continue to take soundings from our beekeepers to see if they report any negative effects on their hives.”