The increased threat of terrorism and a flood of illegal guns into the community have led the Government to establish the first national gun amnesty since the Port Arthur massacre.

Justice Minister Michael Keenan will today announce the details of the three-month amnesty running from July 1.

The amnesty begins amid growing debate about national security, and how people such as Lindt Cafe siege gunman Man Haron Monis got access to weapons.

"Clearly the fact [is] we've got a deteriorating national security environment, we've got an environment where there has been five terrorists attacks on our soil and sadly in the vast majority of those cases it has been an illegal firearm that's been used," Mr Keenan told the ABC.

"Clearly that makes this top of mind and why we want to make sure we can clear as many illegal firearms from the community as possible."

'No questions asked, no repercussions'

Mr Keenan maintains Australia's gun laws are some of the strongest and most effective in the world, but there are still serious concerns about the number of illegal weapons in the community.

"We know that we've got a big illicit firearm market in Australia, 260,000 illicit guns we believe are out there," he said.

"It might be a family heirloom, it could be the family member who owned it has died for example and the family just doesn't know what to do with it.

"So we want to give people an opportunity to hand in their guns, no questions asked, no repercussions.

"We don't want those guns to be able to fall into the wrong hands."

In 1996, gunman Martin Bryant murdered 35 people and wounded 23 others at the Port Arthur historic site in southern Tasmania.

Then prime minister John Howard responded with tough gun ownership laws and a national amnesty.

Mr Keenan argued subsequent state amnesties, such as in Queensland, had proven a successful way to clean up the streets.

"One illicit firearm can be very, very dangerous and the less illicit firearms we have in the community, the safer our community is going to be," he said.

"There does appear to have been a proliferation of illicit guns over time, but remember there used to be a lot of guns in Australia until we've had very strict gun laws that were instituted after the Port Arthur massacre in 1996."

People caught outside the amnesty period with an unregistered firearm could face fines of up to $280,000 or up to 14 years' jail.

Amnesty 'wont stop terror threat'

The vice-president of Gun Control Australia, Roland Browne, said the amnesty would not do anything to combat terrorism.

"Amnesties are good in the sense that they take guns out of the hands of the community who don't need them and that's especially helpful in the case of suicide," Mr Browne told The World Today.

"But if you are dealing with people who are hellbent in causing terror, they are not going to hand in their guns.

"Introducing an amnesty is an easy fix, it is not a backwards step, but it is not actually solving the problem and the problem is guns moving out of the hands of legal users into those who shouldn't have them."

Mr Browne said there was no need for individuals to build up personal arsenals.

"There are too many instances of gun thefts of 10, 12, 15 guns at a time. People do not need that number of guns in their homes," he said.

"There are going to have to be limits in place on the number of guns in homes."