The number of people with a mental illness police are dealing with each year has grown massively over the past decade, as the force seeks to renegotiate its frontline role in dealing with mental illness.

In the year 2000, police invoked the Mental Health Act – giving them power to take people to hospital if their mental state presents a threat – fewer than 3000 times. That number reached slightly fewer than 50,000 times last year, new figures show. A 2010 study found that about half the time the Act was invoked, police transported a person to a mental health facility.

Police attribute the huge spike to the rising use of drugs such as crystal meth, officers becoming better at recognising mental illness and the effects, two decades on, of a shift in government policy to release people with mental illness into the community.

Professor Ian Hickie, from Sydney University's Brain and Mind Institute, said the rise owed to a failure of mental health care in the community and overstretched hospitals possibly discharging patients early.