People who use electronic cigarettes, which are widely promoted and used to help smokers quit traditional cigarettes, are actually 28 per cent less likely to kick the butt, a new study has warned.

Electronic cigarettes, known by a variety of names including vapour pens, are battery-powered devices that heat nicotine and flavourings to deliver an aerosol inhaled by the user.

While they are promoted as a way to quit traditional cigarettes, they also are promoted as a way to get nicotine in environments where traditional cigarettes are prohibited.

Researchers at the University of California in San Francisco (UCSF) reviewed 38 studies assessing the association between e-cigarette use and cigarette cessation among adult smokers.

They then combined the results of the 20 studies that had control groups of smokers not using e-cigarettes in a meta-analysis that concluded that the odds of quitting smoking were 28 per cent lower in smokers who used e-cigarettes compared to those who did not.

The studies included smokers who both were and were not interested in quitting, and included people as young as 15 years old.

The studies included in the analysis controlled for many variables, including demographics, past attempts to quit, and level of nicotine dependence.

"The irony is that quitting smoking is one of the main reasons both adults and kids use e-cigarettes, but the overall effect is less, not more, quitting," said Stanton A Glantz from UCSF.

"While there is no question that a puff on an e-cigarette is less dangerous than a puff on a conventional cigarette, the most dangerous thing about e-cigarettes is that they keep people smoking conventional cigarettes," he added.

The findings were published in the journal The Lancet Respiratory Medicine.