Pesticides developed to replace banned bee-killing insecticides have been found to reduce colonies by half.

It was hoped that sulfoxaflor would provide an alternative to neonicotinoids, which have been shown to drastically reduce bee numbers, and is currently under review for licencing in Britain.

But researchers at Royal Holloway, University of London found exposure to the new pesticide reduced both the size of bumblebee colonies and the number of offspring produced by 54 per cent.

Doctoral student Harry Siviter said: “Neonicotinoids are the most commonly used insecticide in the world, but the evolution of resistance by pests, as well as bans and restrictions on their usage has resulted in a demand for alternative pesticides.

“Sulfoximine-based insecticides are a likely successor and are being registered for use globally.

“Our results show that sulfoxaflor can have a negative impact on the reproductive output of bumblebee colonies under certain conditions.”