Drug companies are sponsoring more and more groups for patients in Germany to increase demand for their products, but many members remain unaware of their involvement, a study has found.

The firms are also advertising their products on what seem to be independent websites, despite laws that ban advertising prescription medicines to the public.

The study, by the Zentrum für Sozialpolitik of Bremen University, was commissioned by Germany's state health insurance companies and focused on the funding of groups for patients with chronic diseases, such as Alzheimer's disease and eczema.

At present, health insurance companies are the main sponsor of patients' groups, spending a total €28m (£19m; $37m) in 2005, but drug companies are increasingly moving into the area.

A quarter of patients' …