Almost twice as many older Australians are using illegal drugs, with increasing numbers of people aged 60 and over reaching for illicit substances like cannabis and black market pharmaceuticals.

An Australian Institute of Health and Welfare (AIHW) report released on Tuesday shows the proportion of people aged 60-something who recently used illicit drugs increased from 3.9 per cent to 6.9 per cent in the 15 years to 2016.

Some older people are finding themselves dependent on opioid painkillers and benzodiazepines like Valium after being prescribed these drugs by a doctor. Credit:AP

Alcohol and Drug Foundation spokeswoman Melinda Lucas said the figures reflected an "ageing cohort" of drug users who had not given up substances in the same numbers as the generations that preceded and followed them.

"Also, as we start to see a lot more interest in people using cannabis for medical purposes, a lot of people report using cannabis medically but unprescribed," Ms Lucas said. "Society has changed in how we view cannabis; support for legalisation has significantly increased and there is less stigma."