The organic farming organisation said Italy had joined Germany, France and Slovenia, in clamping down on the substances in the interests of bees.

The Italian Embassy confirmed its government had banned the use of neonicotinoids and a related substance as seed treatments, although not as sprays, for reasons including feed-through into bees.

Soil Association policy director Peter Melchett wrote to the Secretary of State for the Environment, saying: "Colony Collapse Disorder is not just a problem for beekeepers and farmers, but for consumers as well, since bee pollination is essential for crop production.

"The products implicated in bee deaths – clothianidin, imidacloprid, fipronil and thiamethoxam – are approved to kill insects on a wide range of crops in the UK, including oilseed rape, barley, and sugar beet. Oilseed rape is of particular concern, as the flowers are very attractive to honey bees.

"Since their introduction by Bayer CropScience in the USA in 2003, neonicotinoids have been link-ed to the devastating loss of millions of honey bees in a number of countries."

But a Bayer spokeswoman said: "Extensive monitoring programmes in Germany, France, Italy and Belgium have not shown any significant impact from the use of pesticides ... except when products were used incorrectly."

The British Bee Keepers Association said the Soil Association was mixing up two different problems and a ban on neonicotinoids would not help.

Mike Harris, general secretary of the British Bee Keepers Association, said Colony Collapse Disorder was caused by the varroa parasite. Pesticides were a separate problem – and in the UK, at least, neonicotinoids were not normally used in concentrations harmful to bees.

Mr Harris said: "We are realistic about farmers' needs and if they stopped using these chemicals tomorrow, it would not help much."

The pesticides in question could be banned, anyway, however, under a proposed new EU law – although the Government is contesting it.