SCIENTOLOGISTS have been bombarding NSW MPs with letters urging them not to make psychiatric drugs more available as part of an orchestrated campaign to stamp out their use.

But not one of more than 120 letters obtained by the Daily Telegraph identifies the author as a Scientologist despite many coming from its inner-west offices.

The move has raised serious concerns about religious groups or cults lobbying governments and politicians for a change in the law without identifying their links.

The practice has particular resonance after revelations a young woman who allegedly killed her sister and father and critically wounded her mother after her parents denied her access to psychiatric medication.

Several letters, under different names, come from the same address in Five Dock, listed on several websites as the "Inner West Mission" of the Church of Scientology.

The Australian Medical Association said if the individuals were writing on behalf of a religious organisation or as a result of their religious beliefs they ought to disclose that.

Mental Health Minister Paul Lynch said Scientologist representations could not outweigh expert evidence and opinion.