Less than two weeks after the Port Arthur massacre, Australia banned semi-automatic rifles and shotguns. New Zealand similarly banned a range of semi-automatic firearms after a lone gunman killed 50 worshippers in two Christchurch mosques on March 15.
Morrison said his conservative Liberal Party would disadvantage One Nation candidates under Australia's preferential voting system at general elections due in May by refusing to share votes. Under Australia's systems, voters rank candidates in order of preference. The higher candidates are ranked by a majority of voters, the better their chances of being elected.
The Liberal Party would normally direct its supporters to rank the opposition center-left Labor Party last, because Labor candidates have a chance of forming government. Like-minded parties often make deals to rank each others' candidates ahead of a common enemy.
But in a move interpreted by some as putting principle ahead of politics, Morrison said his party would urge voters to rank Labor ahead of One Nation. "This is a decision which is based on our strong view about the sanctity of Australia's gun laws and to ensure that at no stage that those things should ever be put at risk," Morrison told reporters.
"It's very important, having been the party that introduced those laws, that we ensure that they are forever protected and there can be no compromise when it comes to those issues or any trading on the issue of those gun laws," he added.
Anti-Muslim One Nation has been widely condemned after an Al Jazeera documentary reported this week that two party officials flew to the United States for meetings with pro-gun interests including the National Rifle Association and political donors Koch Industries in September last year seeking money to undermine Australian gun laws.
The two-part documentary that uses video secretly filmed by a fake gun lobbyist reveals Hanson said during a dinner with party officials in her home state of Queensland last year that she has "a lot of questions" about the Port Arthur massacre.
She quoted an Australian state premier who said almost a decade before the mass shooting in the ruins of a 19th century Tasmanian prison: "It will take a massacre in Tasmania before we get gun reform in Australia."
Conspiracy theorists argue the quote proves that the massacre was engineered by the gun reform lobby. Others argue the quote reflects a New South Wales premier's frustration that Tasmania had Australia's weakest gun laws and was most resistant to change. Australia now has relatively uniform gun laws.
While on the subject of conspiracy theories, a party official at the dinner is recorded mentioning the al-Qaida attacks on the United States on Sept. 11, 2001. Hanson said on Thursday her broadcast comments has been "heavily edited" and did not reflect her views on the Australian massacre.
"There is no question in my mind that Martin Bryant was the only person responsible for the murders of 35 innocent lives," Hanson told reporters, referring to the convicted killer. "Let me make it very clear to everyone in this country: One Nation will never water-down gun policy in this country," she added.
She described Morrison as "a fool" who would give Labor the government at the next election through his decision on vote-sharing. Morrison said Hanson's broadcast comments on the Port Arthur massacre, to which the gunman pleaded guilty, was the final straw. He said he consulted former Liberal Prime Minister John Howard, who introduced Australia's gun reforms and a buyback that reduced the estimated number of guns in Australia by 20 percent, before announcing his decision.
Barnaby Joyce, a senior lawmaker in the Nationals party, the rural-based junior partner of the ruling coalition that most directly competes against One Nation for conservative voters, described Hanson's comments on Port Arthur as "bonkers mad."
"It is beyond the pale. We now have One Nation questioning both 9/11, the terrorist attack on New York and the Port Arthur massacre," Joyce told Australian Broadcasting Corp. "What is next for them? Are they going to question man on the moon? "
The Nationals have yet to say whether they will follow the Liberal Party lead by putting Labor ahead of One Nation on how-to-vote cards distributed at polling booths to its supporters. One Nation has accused Qatar-owned Al Jazeera of breaching new laws that prohibit covert foreign interference in Australian politics.
Al Jazeera said it stood by its reporting and that its journalists "adhere to the highest standards of professionalism and objectivity."