The European Food Safety Authority (EFSA) proposed that safe levels for exposure be lowered while further research is carried out.
They based their decision on studies that showed the chemicals had an impact on the brains of newborn rats.
One of the pesticides was banned in the EU last April amid concerns over its impact on bee populations.
Neonicotinoids are “systemic” pesticides that make every part of a plant toxic to predators.
They have become very popular across the world over the past two decades as they are considered less harmful to humans and the environment than older chemicals.
But a growing number of research papers have linked the use of these nicotine-like pesticides to a rapid fall in bee numbers.
New levels needed
In April, the European Union introduced a two year moratorium on the use of several types of these chemicals, despite opposition from the UK.
Now EFSA, in a statement, says that it has concerns that two types of neonicotinoids, imidacloprid and acetamiprid, may “affect the developing human nervous system“.
They have proposed that guidance levels for acceptable exposure be lowered while further research is carried out.
The decision has been based on a review of research carried out in rats.
In one study, young rodents exposed to imidacloprid suffered brain shrinkage, weight loss and reduced movement.
In the statement, EFSA said that the two neonicotinoids may “adversely affect the development of neurons and brain structures associated with functions such as learning and memory”.
Current guidelines, it went on, “may not be protective enough to protect against developmental neurotoxicity and should be reduced”.
According to EU Commission health spokesman Frederic Vincent, they would now allow the chemical companies involved to comment on the findings.
“In principle, the next step would then be to amend the reference values,” he said, indicating that this would begin next March.
In their findings, EFSA pointed out that the available evidence had limitations but that they believed the health concerns that have been raised are legitimate.
But other experts said the move by EFSA was more of a precaution than anything else.
“The reduction in the reference values in most cases was modest,” said Prof Alan Boobis, from Imperial College London.
“Whilst there is clearly a question mark over the possible effects of these compounds on the developing brain, the conclusions of EFSA do not suggest that exposure of humans to these compounds at the levels that occur normally in food or in the environment is a cause for concern.