There are renewed calls for the Coalition to preference One Nation last at the federal election following revelations the party's leader Pauline Hanson appeared to question the 1996 Port Arthur massacre, which left 35 people dead after a gunman went on a rampage in Tasmania.

Key points: Pauline Hanson said there were "a lot of questions" surrounding the Port Arthur massacre

Pauline Hanson said there were "a lot of questions" surrounding the Port Arthur massacre Her comments were met with outrage, with the MP representing Port Arthur saying she was not fit to be in Parliament

Her comments were met with outrage, with the MP representing Port Arthur saying she was not fit to be in Parliament Senator Hanson was unavailable for comment

Her comments have prompted Liberal backbencher John Alexander, who represents the electorate former prime minister John Howard once held, to predict his party would have to preference One Nation last at the election.

"That will most likely be the case unless there's somebody worse [than One Nation] but it's unlikely you'd find somebody worse," he said.

"This group is self-destructing."

The footage, taken as part of an Al Jazeera documentary, also revealed senior figures of the party wanted millions of dollars in donations from America's National Rifle Association and discussed softening its policies on gun ownership as it tried to secure the funding.

The second instalment of the documentary showed Senator Hanson discussing Port Arthur with her chief of staff James Ashby and undercover journalist Rodger Muller at a dinner in the central Queensland town of Yeppoon.

"An MP said it would actually take a massacre in Tasmania to change the gun laws in Australia," she told Mr Muller, who was posing as a gun rights advocate to infiltrate the group.

"Have you heard that? Have a look at it. It was said on the floor of Parliament.

"Those shots, they were precision shots … they didn't muck around … I read a book on it, on Port Arthur. A lot of questions there."

Former NSW premier Barry Unsworth was the MP who originally made the statement in the 1980s, and the quote is a popular one among internet conspiracy theorists who believe the killer was set up so Australia would tighten its gun laws.

The recorded comments were met with outrage, with federal Labor MP Brian Mitchell, who represents Port Arthur, saying Senator Hanson was not fit to be in Parliament.

"Pauline Hanson is not fit to represent the Australian public, in the Senate in the Parliament or anywhere," he said.

"She's a disgrace, she's an absolute disgrace and she has no place in the Parliament.

"And I would urge every Australian, young and old, to make sure One Nation's put last on every ballot paper around the country."

'An awful, awful tragedy'

Federal Labor MP Andrew Leigh said his mentor, lawyer Zoe Hall, was one of the victims of the Port Arthur massacre.

"It's frankly just disgusting to me that anyone would suggest that this is some kind of hoax," he said.

"It was an awful, awful tragedy in which wonderful Australians died."

Mr Howard brought in strict gun controls and a buyback after Port Arthur and then demanded One Nation be preferenced last at the 2001 election.

Dr Leigh said One Nation was too far outside the political mainstream for any of the major parties to be "conniving with".

"And yet still Scott Morrison is refusing to put them last on how-to-votes as John Howard did," he said.

"If Scott Morrison was a strong leader he would follow the example of John Howard and put One Nation last, where they belong, in every contest and every candidate, Liberal and National."

Mr Morrison has repeatedly said he would wait until all candidates had been declared for the election before deciding where to preference One Nation.

Vice president of Gun Control Australia Roland Browne said it was "cruel" to be raising the issue now, a month shy of the massacre's 23rd anniversary.

He said the man responsible for the killings pleaded guilty and acted alone.

"At no time has he suggested anybody put him up to this, and apart from Pauline Hanson and a right-wing conspiracy theorist on the internet, nobody else has suggested that he was put up to this," he said.

Senator Hanson was unavailable for comment.

In 2001, she said conspiracy theories about Port Arthur were ridiculous but she has not responded to the latest developments.

Watch the second part of the Al Jazeera investigation on tonight on ABC TV or watch the full documentary on iview.