What the independent evidence tells us about nicotine
It’s widely accepted that nicotine is not the cause of smoking-related diseases.
We have known for years that people smoke for the nicotine, but die from the smoke."
Reducing the toll of death and disease from tobacco, open letter to the WHO signed by 53 leading scientists and public health experts, May 2014
Nicotine: The facts
Nicotine occurs naturally in tobacco leaf and significantly lower levels are also found in plants such as tomatoes, potatoes and aubergines (eggplant).
Nicotine products, as an alternative to conventional cigarettes, are considered to offer significantly reduced health risks.
It is largely the toxicants found in cigarette smoke that cause the overwhelming majority of smoking-related diseases – not the nicotine itself.
Nicotine inhaled from smoking tobacco is highly addictive. But it is primarily the toxins and carcinogens in tobacco smoke – not the nicotine – that cause illness and death."
Tobacco harm reduction approaches to smoking, UK National Institute for Health and Care Excellence, public health guidance 45, July 2013
What the independent evidence tells us about e-cigarettes
Evidence suggests e-cigarettes are significantly less risky than smoking.
In a study on behalf of the UK-based Independent Scientific Committee on Drugs, a panel of global experts in the field of nicotine and tobacco research used a multi-criteria analysis to rank tobacco and nicotine products based on harm to users and harm to wider society. The study attributed a relative harm score of 100% to conventional cigarettes, while giving a score of 4% for e-cigarettes. 
The chemicals that make cigarettes dangerous are either absent in electronic cigarettes or present only in trace concentrations."
Should e-cigarettes be regulated as a medicinal device? P Hajek et. al., The Lancet, July 2013
Studies suggest e-cigarettes can help people quit smoking, while there is currently little evidence that they’re a gateway into smoking.
Many recent studies  have found that regular e-cigarette use among people who’ve never smoked is negligible at under 1%.
While it is important to control the advertising of electronic cigarettes to make sure children and non-smokers are not being targeted, there is no evidence from our research that e-cigarettes are acting as a gateway into smoking."
Action on Smoking and Health UK, press release on e-cigarette research, April 2014