Defra is being investigated over its emergency authorisations of a neonicotinoid pesticide in 2023 and 2024.
The Office for Environmental Protection (OEP) confirmed it had launched an investigation into the department.
The body, which was only launched in 2021, is seeking to determine whether there were serious failures in Defra's compliance with environmental laws.
The move is in relation to two emergency authorisations granted for the use of Cruiser SB (thiamethoxam) on sugar beet seeds in 2023 and 2024, under the previous Conservative government.
In particular, the OEP said its investigation would look at Defra’s interpretation and application of the precautionary principle.
It said it was also looking into Defra's compliance with its nature conservation obligations when granting emergency authorisations.
The OEP's investigation has launched after it received a complaint submitted by ClientEarth, an environmental law group.
