People who have used electronic cigarettes say they were a bit helpful to quit smoking, but the devices were described as unreliable, Swiss researchers say.

Study author Jean-Francois Etter of the University of Geneva in Switzerland says the study involved surveying 81 users and former users of e-cigarettes.

Ninety-five percent say the e-cigarettes were at least somewhat helpful to stop smoking.

However, some said they were concerned about potential toxicity and some described the devices as "poor quality," "lack of reliability" and "frequent failures."

"Although users' comments were generally positive, many were concerned about safety and toxicity and questioned why no study has yet investigated these aspects," Etter says in a statement.

"Several respondents were also concerned about the future legal status of e-cigarettes, and that they may possibly be banned. Very few studies have investigated these devices and research is now urgently required. There is an urgent need for research into the toxicity, efficacy and public health impact of e-cigarettes."

The findings are published in the BMC Public Health.