Information about NHS services is not getting through to certain sections of the British public, according to a report.
Research by the University of Birmingham's Health Services Management Centre shows that most patient information is provided in the form of written leaflets or via the internet.
But studies show that around one in five Britons do not have basic literacy and struggle to read, while a third of households are not connected to the internet.
This means many people are not able to access or understand information which could help them use the health services more effectively, flying in the face of the government's policy of encouraging patient choice.
Report author Jo Ellins said: "The NHS recognises that information is essential to support patient choice and it is committed to making more information about health services publicly available.
"But the way in which this information is currently provided restricts opportunities for informed choice to more educated and affluent patients. There is a very real danger that this is sustaining, or even increasing, health inequalities."