As the UK government moves to ban sales of electronic cigarettes to anyone under 18, a group of leading scientists has warned the EU that tougher controls within its Tobacco Products Directive could act as a further deterrent to smokers trying to quit.

In an open letter to health commissioner Tony Borg, the global panel of 15 leading academics claim the directive overstates the toxicity of nicotine and puts too low a limit on the amount of nicotine that should be allowed in an e-cigarette.

The TPD states that the acute lethal dose of nicotine in an adult human is about 60mg. However, the scientists argue this claim is erroneous and can be “traced to dubious self-experiments recorded in a pharmacology textbook of 1856 and not confirmed since then”.

They add that the EU based its decision to limit the level of nicotine in an e-cigarette to 20mg on this assumption.

The directive also suggests that 20mg is similar to the amount of nicotine in a standard cigarette. The scientists, however, contend that 20mg of e-liquid contains less than one third of the nicotine of a conventional cigarette and that 50mg would be a closer match.

Smokers who are looking to quit typically turn to e-cigs with a higher nicotine content, they add, and lowering the limit would put them off.

The scientists also reject the UK government’s assertion last week that e-cigs could act as a gateway to smoking. “The evidence is instead that the gateway effect is out of tobacco use,” they argue in the letter.

Topics