HOSPITAL chiefs say they will do everything they can to stop pregnant women from smoking for the good of their health and that of their unborn child.
But health experts have expressed strong concerns.
An e-mail leaked to the Daily Post and written by a senior NHS adviser says smokers may just smoke more to compensate for the missing nicotine.
It adds: "Unless there is clear evidence that people do cut down as a result of using the product, then on safety and ethical grounds its use in pregnant women is strongly contradicated."
The report by regional NHS smoking cessation advisers, obtained by the Daily Post, says the focus on the effects of smoking in pregnancy on the health of the woman, unborn child and immediate family, which this trial at Liverpool Women's Hospital has brought about, is to be welcomed.
But it says there are other factors which need to be considered.
It states that the use of the fluid block 'ignores the fact that the smoking 'habit' is not only an addiction but part of a cultural norm and therefore will continue as long as that social pressure is not addressed'.
It also says the effects of using the fluid on tobacco smoke in the environment are not known and adds: "Many pregnant women have young children therefore passive smoking will be a risk."
The Department of Health also says it does not recommend the use of NicoBloc because of the lack of evidence.
A spokeswoman said: "We understand Liverpool Women's Hospital have started up a local study of the effectiveness of a product called NicoBloc.
"At present, there is little independent evidence of its efficiency in reducing tobacco addiction and we could not recommend its general use. We recommend the proven NHS smoking cessation services are utilised."
But the hospital say NicoBloc is a very safe product which can give women who are trying to stop smoking the added help they need.