Prime Minister Scott Morrison has defended a preference deal with Senate hopeful Clive Palmer, saying the options on the ticket were "pretty thin" and arguing that the Queensland minerals magnate was less of a risk to the Australian economy than the Labor Opposition.

Key points: Preference deals with One Nation and the United Australia Party could prove instrumental in tipping marginal seats

Preference deals with One Nation and the United Australia Party could prove instrumental in tipping marginal seats Scott Morrison says the Nationals' decision to swap preferences with One Nation in some seats is a matter for their party

Scott Morrison says the Nationals' decision to swap preferences with One Nation in some seats is a matter for their party Mr Morrison also accuses Greens leader Richard di Natale of supporting vegan activists who broke into farms

In an extended pre-election interview with 7.30 host Leigh Sales, Mr Morrison was pressed on the Coalition's preference arrangements with minor parties.

The deals with One Nation and Mr Palmer's United Australia Party could prove instrumental in tipping marginal Queensland seats — some of which were decided based on minor party preference flows at the last election.

"Once you vote Liberal/National, the choice after that gets pretty thin," Mr Morrison said.

"Do I think the United Australia Party is a bigger risk to the Australian economy and jobs and Australia's future than Labor and the Greens? No, I don't think they're a bigger risk."

Mr Morrison went on to criticise Greens leader Richard di Natale, accusing him of supporting vegan activists who made headlines with a string of farm break-ins last month.

"Richard di Natale thinks it's OK for people to invade farms. So I don't think that's terribly sensible. Richard di Natale supports death taxes, I don't think that's particularly sensible," Mr Morrison said.

While some in the Greens have defended the activists' right to protest, Senator di Natale is on record as saying the laws of trespass should be respected.

"If people break the law then clearly they need to face the consequences of those actions," the Greens leader said in April.

Will Abbott, Turnbull attend Liberal launch?

The official Labor campaign launch at the weekend saw former prime ministers Kevin Rudd and Julia Gillard sitting side by side, smiling for the cameras in an apparent display of unity as Opposition Leader Bill Shorten outlined his election promises.

Mr Morrison was asked if voters could expect a similar display from Tony Abbott and Malcolm Turnbull at the Liberal launch, to be held this weekend in Melbourne.

Julia Gillard and Kevin Rudd reunited at the weekend in an apparent display of unity. ( ABC News: Andy Kennedy )

The Prime Minister would not be drawn on whether the former PMs would attend.

"My launch on Sunday is going to be different ... it's not a party hoopla," he said.

"It's not about who is coming, it's about who is listening."

The toppling of Mr Turnbull was a "matter of record and history now", he said.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 19 minutes 5 seconds 19 m Watch Prime Minister Scott Morrison's full interview with 7.30's Leigh Sales.

One Nation deal a matter for 'separate' Nationals

The Prime Minister was also quizzed about the Nationals' decision to swap preferences with One Nation in some seats.

"That's a matter for the National Party, they're a separate party, Leigh," Mr Morrison said.

While the Liberals and the Nationals cooperated when they were in Coalition government together, the Prime Minister said they made "separate decisions about political matters".

Asked if he had expressed any "dissatisfaction" with the decision, Mr Morrison replied: "I respect the National Party to make their own decisions and they can explain those decisions themselves."

Who will control the Liberal party room?

Mr Morrison was asked who would have the "upper hand" in controlling the Liberal party room under a future Morrison government — the "mainstream" moderates of the Liberal Party, or the right-wing faction that orchestrated the effort to dump Mr Turnbull.

He gave a two-word reply: "I will."

Mr Morrison conceded carbon emissions had "lifted" during the Coalition's time in government, but repeated his promise to meet Australia's reduction targets under the Paris agreement.