The environmental watchdog has launched an investigation into the Government’s emergency authorisation of a banned pesticide toxic to bees.

The Office for Environmental Protection (OEP) said it was seeking to determine if there were “serious failures” to comply with environmental laws when the Environment Department (Defra) granted the use of neonicotinoid Thiamethoxam on sugar beet seeds in 2023 and 2024.

The pesticide, which is lethally toxic to bees, was banned in the UK and EU in 2018.

Failing to take a proper precautionary approach when approving the use of pesticides is threatening our pollinators and the wider environment - and puts England even further off-track from meeting its 2030 biodiversity targets

It was approved for emergency use in the UK for a fourth year in a row in January, sparking anger from environmental groups who described it as a “death blow” to the pollinating insects.

The Government said the neonicotinoid could be used on sugar beet “because of a danger that cannot be contained by any other reasonable means”.

Farmers use the pesticide to kill aphids that can spread the beet yellows virus and the Government said it wanted to protect their livelihoods.

The OEP said it was looking into failures in relation to applying the “precautionary principle”, which helps decision-makers manage the risk of serious harm to the environment, when there is a lack of scientific certainty about the damage it could cause.

It is also looking at failures to meet nature conservation obligations.

The investigation is responding to a complaint by ClientEarth, an environmental legal charity, and a formal letter was sent to Defra on June 14, but could not be made public in the pre-election period.

The emergency authorisations were issued under the previous Tory government and Labour has said it will end the temporary exemptions on the ban of “bee-killing” neonicotinoid pesticides.

A spokesperson for Defra said: “We are at a crisis point – nature is dying across Britain.

“This government will change existing policies to ban the use of bee-killing pesticides to protect our vital pollinators.”

ClientEarth’s Kyle Lischak described the move as a “very welcome first step”, accusing the Government of giving the pesticide the green light for widespread “emergency use” for four consecutive years, bypassing laws designed to protect the environment.

He added: “Failing to take a proper precautionary approach when approving the use of pesticides is threatening our pollinators and the wider environment – and puts England even further off-track from meeting its 2030 biodiversity targets.

“This investigation also sends an important signal to government and other decision-makers: laws that protect nature – such as the Habitat Regulations – have to go beyond planning decisions and include other activities that could threaten nature.

“And while this investigation is under way, we are calling on the new Government to support UK farmers to adopt sustainable methods of pest control that work with nature, rather than putting it at risk – as they are the custodians of so much of England’s natural environment.”