Neonicotinoids, the world’s most widely used insecticides, will be banned for use in fields within six months.

A near total ban on pesticides linked to a decline in bees will come into force in the EU by the end of the year.

Members states have backed the ban on the outdoor use of “neonicotinoid” pesticides, following an assessment by the European Food Safety Authority (EFSA) which found in February they posed a risk to bees.

Use of three pesticides was already restricted in the EU on crops such as oilseed grape, because of concern they have “sub-lethal” effects including damaging bees’ ability to forage or form colonies.

But they could still be used on sugar beet, various horticultural crops and as seed treatment for winter cereals.

Campaigners have warned that the pesticides are contributing to falling populations of bees.

Darryl Cox, senior science and policy officer for the Bumblebee Conservation Trust, said: “Neonicotinoid pesticides are really good at doing what they are designed to do, they are applied to seeds, spread throughout the tissues of an entire plant, and kill off any pests which try to eat it.

“Unfortunately, the active chemicals also accumulate in the pollen and nectar of plants and so reach the diets of non-target, beneficial insects like bees.

“Consuming these contaminants does not always have an acute impact on a bee, however, research has shown that as bees regularly consume neonicotinoids, they and their colonies suffer a range of negative effects, most importantly, on their ability to reproduce.”

The ban however presents a new challenge for farmers, who have used neonicotinoids on their crops to keep away pests.

Guy Smith, deputy president of the National Farmers’ Union, said: “This decision doesn’t change the fact that farmers will continue to face challenges to maintain sustainable and productive cropping systems, and the pest problems that neonicotinoids helped farmers tackle have not gone away.”

Mr Smith added that implementing a more sustainable method of farming would be beneficial for both farmers and conservationists.

He said: “What is needed is a move towards truly sustainable farming methods that minimise pesticide use, encourage natural enemies of crop pests, and support biodiversity and healthy soil.”

Environmental campaigners have welcomed the EU ban.

Emi Murphy, bee campaigner at Friends of the Earth, said: “This a major victory for science, common sense and our under-threat bees.”

Bee populations have been declining steadily for the past 20 years.

A survey conducted by the British Beekeepers Association in 2017 revealed that bee hives in England were producing 11.8kg of honey, whereas a single hive could produce upwards of 25-45kg in the 1950s.