A bee-killing pesticide so poisonous that it is banned by the EU may be used on sugar beet in England, the government has announced.

The decision prompted fury from nature-lovers and environmentalists, who accused ministers of bowing to pressure from farmers.

They said during the biodiversity crisis, when at least half the world’s insects have disappeared, the government should be doing everything it could to save bees, not allow them to be killed.

Environment secretary George Eustice has agreed to let a product containing the neonicotinoid thiamethoxam to treat sugar beet seed this year in an effort to protect the crop from a virus.

Last year a virus significantly reduced sugar beet yields, and similar conditions this year would be likely to present similar dangers, Mr Eustice’s department said.

Setting out conditions for the “limited and controlled” use of the pesticide, officials said the minister had agreed an emergency authorisation of it for up to 120 days. British Sugar and the National Farmers Union had applied to the government to be allowed to use it.

But the Wildlife Trusts said neonicotinoids pose a significant environmental risk, particularly to bees and other pollinators.

A 2017 study of 33 oilseed rape sites in the UK, Germany and Hungary found a link between higher levels of neonicotinoid residues and lower bee reproduction, with fewer queens in bumblebee hives and fewer egg cells in solitary bee nests.

The following year, the EU agreed a ban on all outdoor uses of three neonicotinoid insecticides to protect bees.

Evidence suggests the pesticides harm bee brain development, weaken immune systems and can leave bees unable to fly.  

A 2019 report by the UN Food and Agriculture Organisation and the World Health Organisation said there was a “rapidly growing body of evidence” that “strongly suggests that the existing levels of environmental contamination” by neonicotinoids were causing “large-scale adverse effects on bees and other beneficial insects”.  

The Wildlife Trusts tweeted: “Bad news for bees: The Government has bowed to pressure from the National Farmers Union to agree the use of a highly damaging pesticide.

“The government know the clear harm that neonicotinoid pesticides cause to bees and other pollinators and just three years ago supported restrictions on them across the European Union.

“Insects perform vital roles such as pollination of crops and wildflowers, and nutrient recycling, but so many have suffered drastic declines.”

The trusts added that evidence suggests the world has lost at least 50 per cent of insects since 1970, and 41 per cent of insect species were now threatened with extinction.

“We need urgent action to restore the abundance of our insect populations, not broken promises that make the ecological crisis even worse.”

The Department for Environment, Food and Rural Affairs said sugar beet was cultivated in only one out of four beet-processing factories in the east of England.

Last month it was revealed that the National Farmers’ Union had organised a letter from members to Mr Eustice urging him to allow the neonicotinoid called Cruiser SB to be used in England this spring.

A message to members stated: “Engagement on this campaign has been truly incredible”, adding: “Please refrain from sharing this on social media.”

Thiamethoxam is designed protect sugar beet in its early stages from insects but critics warn it will not only kill bees but also harm creatures in the soil as it washes off.

NFU sugar board chairman Michael Sly said the pesticide would be used in a limited and controlled way and only when the scientific threshold has been independently judged to have been met.

“Virus yellows disease is having an unprecedented impact on Britain’s sugar beet crop, with some growers experiencing yield losses of up to 80 per cent, and this authorisation is desperately needed to fight this disease. It will be crucial in ensuring that Britain’s sugar beet growers continue to have viable farm businesses,” he said.

A Defra spokesperson said: “Emergency authorisations for pesticides are only granted in exceptional circumstances where diseases or pests cannot be controlled by any other reasonable means. Emergency authorisations are used by countries across Europe.

“Pesticides can only be used where we judge there to be no harm to human health and animal health, and no unacceptable risks to the environment. The temporary use of this product is strictly limited to a non-flowering crop and will be tightly controlled to minimise any potential risk to pollinators.”