A protest has taken place in Sydney against moves to introduce a new payment scheme for visits to a doctor.

A crowd of more than 100, wielding signs, political flags and strong opinions, descended on Town Hall on Saturday to protest against a proposal to charge a fee for GP visits.

The outcry follows a co-payment proposal received by the National Commission of Audit in December.

Doctor groups and political parties have said such a move would destroy Medicare.

“To put a barrier in front of people … is trying to make the books balance on some of the poorest and most vulnerable people in this country,” acting Greens leader Richard Di Natale told reporters at the rally.

Penrith student Aislynn Kearney said she relied on Medicare to afford mental health and medical treatment.

GP visits would be in jeopardy under a co-payment scheme.

“I would find myself in a situation where I couldn’t afford treatment,” she told AAP.

Health Minister Peter Dutton told Fairfax Media on Saturday the health system was heading to a point where it would become unmanageable unless it was strengthened.

The federal government has said it would not speculate on what the Commission of Audit may or may not recommend.