The Greens have written to the President of the Senate opposing armed guards being stationed inside both chambers of Parliament.
"More guns don't make people safer," Greens Leader Christine Milne said.
"Australians don't want militarisation of our public spaces, which includes Parliament.
"The Greens do not support firearms being carried anywhere inside the building.
"It has been a long-standing practise in the Westminster system that no arms are to be carried in the Parliament."
Australian Greens spokesperson for legal affairs Senator Penny Wright said the new measures would create unnecessary fear in the community.
"What kind of message are we sending if we say Parliamentarians can't go about their business without being surrounded by armed security?
"We don't want to go the way of America where it's claimed that only a good guy with a gun can stop the bad guys - that's never been the case in Australia and it shouldn't start now."