Federal Justice Minister Michael Keenan says the government has no plans to change the national gun control laws.

His comments come after former prime minister John Howard, who introduced the laws 20 years ago after the Port Arthur massacre, told SBS' Insight program on Tuesday night they needed to be strengthened.

"There's no plans to change what has been a very successful gun control agreement in Australia," Mr Keenan said in Brisbane on Wednesday.

In a charged debate on Tuesday night, Mr Howard was questioned by the son of killed police worker Curtis Cheng as to whether the the current gun laws were strong enough.

"Are our gun laws adequate in protecting us?" Alpha Cheng asked. "Are we as safe as we think we are?"

Mr Howard responded that "almost certainly the answer to that question is no: the gun laws are not adequate."

Referring to Curtis Cheng's young killer, he queried the the efficacy of the laws where a 15 year-old could access weapons such as the one used to kill the accountant.

"I am wholly against the watering down of the existing laws, and I would encourage sensible strengthening of the existing laws," Mr Howard said.

Mr Howard was joined on the show by Port Arthur survivors, ahead of the massacre's twentieth anniversary on 28 April, as well as representatives of the gun community.

A repeat of Insight's episode on gun control in Australia airs this afternoon, 3:30pm SBS or is available online now.