Evidence is mounting that widely-used pesticides harm moths, butterflies and birds as well as bees, adding to concerns crop production could be hit by a shortage of pollinators, according to a report drawn up for EU policymakers.

The European Commission, the EU executive, placed restrictions on three neonicotinoid pesticides from Dec. 1, 2013, citing worries about their impact on bees, but said it would review the situation within two years at most.

The makers most affected include Bayer CropScience and Syngenta.

When the restrictions were agreed, the European Academies' Science Advisory Council (EASAC), a network of EU science academies that seeks to inform EU policymakers, assembled 13 experts to assess the relevant science.

Its report published on Wednesday found there was "an increasing body of evidence" that neonicotinoids, used in more than 120 countries, have "severe negative effects on non-target organisms".

Bees are, generally speaking, the most important crop pollinators.

But the report said relying on one species was unwise and found the attention on bees had masked the impact on other pollinators such as moths and butterflies, as well as birds, which eat some pests.

Citing an increase in crops that require or benefit from pollination, the report noted "an emerging pollination deficit".

Proponents of neonicotinoids say they have a major economic benefit because they destroy pests and help to ensure abundant food for a growing world population.

But the report cited the monetary benefits of protecting pollinators and natural pest controllers.

Some 75 percent of crops traded on the global market depend on pollinators and the value of pollination in Europe is estimated at 14.6 billion euros ($15.9 billion).

Natural pest control, whereby insects, such as wasps and ladybirds, as well as birds consume enough pests to avoid the need for chemical treatment, is estimated to be worth $100 billion annually worldwide.

Neonicotinoids are synthetic chemicals that act systemically, meaning they are absorbed and spread through the plant's vascular system, which becomes toxic for insects sucking the circulating fluids or ingesting parts of it.

The European Crop Protection Association (ECPA), which represents the pesticide industry, said the new report was biased.

In a statement Jean-Charles Bocquet, ECPA Director General, said it reflected "a bias of the anti-neonicotinoid campaign toward highly theoretical laboratory tests rather than fully considering published field studies and other independent research that proves the safety of these pesticides".

The Commission welcomed the report and said it would start a review of new scientific information by the end of May.