An international panel of scientists has called for an "evidence-driven debate" over whether a widely used type of insecticide is to blame for declines in bees and other insect pollinators.

EU restrictions on certain neonicotinoid insecticides was introduced in December 2013 because of fears they are harming pollinating insects. Pollination by insects is critical for many crops and for wild plants but at the same time neonicotinoids are one of the most effective insecticides used by farmers. Potential tensions relating to the the agricultural and environmental consequences of neonicotinoid use have made this topic one of the most controversial involving science and policy.

The EU Commission went ahead with planned restrictive measures on three types of neonicotinoid in December. The decision was supported by the majority of EU Member states, though the UK government has refused to back the latest developments in neonicotinoid science and limited itself to implementing the mandatory aspects of the ban, leaving out certain recommended measures.

Earlier this month the neonicotinoid debate was catapulted back into the headlines when a study by Harvard researchers added further weight to arguments that neonicotinoids are having a detrimental effect on pollinator health.

A restatement of the scientific evidence on neonicotinoids was published in the Proceedings of the Royal Society B on Wednesday (21 May). The restatement, from a group of nine scientists led by Professor Charles Godfray and Professor Angela McLean of the Oxford Martin School at Oxford University, attempts to "clarify the scientific evidence available on neonicotinoids, to enable different stakeholders to develop coherent policy and practice recommendations."

One of the authors, Professor Lin Field from Rothamsted Research, said, "It was a pleasure to work with my co-authors who all have diverse expertises, relevant to the debate over the potential effects of neonicotinoids on pollinators, but all wanted to look at evidence rather than opinion. It is essential that we base decisions in this important area on science, so that we find the best way forward to ensure both pollinator success and good crop protection strategies for food production."

Professor Charles Godfray expanded on areas where research is lacking, "Pollinators are clearly exposed to neonicotinoid insecticides, but seldom to lethal doses, and we need a better understanding of the consequences of realistic sub-lethal doses to the insect individual, bee colony and pollinator population."

Professor Angela McLean added, "A major question to be addressed is what farmers will do now that they face restrictions on the use of neonicotinoids. Will they switch to crops that need less insecticide treatment or might they apply older but more dangerous chemicals?"

The restatement describes how much insecticide is present in a treated plant and how much is consumed by pollinators. It goes on to summarise how neonicotinoids affect individual bees and other pollinators, and the consequences at the colony and population levels.

Reacting to the study, Professor Ian Boyd, Chief Scientific Advisor at Defra said, "It is essential that policies on the use of pesticides are built on sound scientific evidence. This paper provides an independent assessment of this subject which will provide clarity and authority in order to help people make more informed choices."

Paul de Zylva, from Friends of the Earth, also commented, "This project is an important step toward much needed public and scientific debate and scrutiny. The Government should support and fund both more open science and safer ways to grow crops as part of its National Pollinator Strategy due in July."

Key facts

• Since their introduction in the 1990s, the use of neonicotinoids has expanded so that today they comprise about 30% by value of the global insecticide market
• Insects are important for pollinating many UK crops, including strawberry, raspberry, apple, pear, plum, tomato and many vegetables
• The populations of both managed honeybees and wild pollinators were declining before the widespread use of neonicotinoids, with habitat change and honeybee disease thought to be particularly important causes
• A series of experiments have raised the possibility that widespread neonicotinoid use may exacerbate pollinator decline