Environmental groups have repeated calls for neonicotinoid pesticides to be banned because of their damage to honey bee populations.
Neonicotinoid pesticides are a comparatively new group of synthetic chemicals used as a coating for agricultural seeds and in pot plants. The chemicals spread throughout the plant and into the nectar and pollen that bees then eat.
A report from the conservation group Buglife and backed by the Soil Association and Pesticide Action Network UK, has linked the pesticides, widely used on farms and at plant nurseries, to widespread declines in wild bee populations.
The Buglife report shows that bees eating nectar and pollen contaminated with one of the most common neonicotinoid forage less and produce fewer offspring.
Buglife says the current approval process is inadequate and that the use of neonicotinoids should be temporarily suspended.
Similar calls were made last year but Defra said there was not enough evidence to ban the pesticide.
'A number of independent studies show that the pesticides are damaging to bees,' said Bumblebee Conservation Trust Director Dr. Ben Darvill. 'The studies carried out by agro-chemical companies show that they are not damaging.
'My own view is that the sensible precautionary principle should be used until they are proven safe,' he said.
The NFU backed calls for an independent assessment of the impact of neonicotinoids but said it would not support a ban unless there was 'clear evidence' that its use was a factor in the decline in honey bee populations.