The Liberal party has agreed to exchange preferences with Clive Palmer in a deal nutted out by party figures on Wednesday night.

Sources say how-to-vote cards that see the Liberals preferencing the United Australia party are ready to print, with Palmer to be placed ahead of the Labor party in lower-house seats and in the Senate.

The deal could prove critical to the outcome in a host of marginal seats across the country, and improves the chances of Palmer reclaiming a spot in the Senate where his resurrected party could hold the balance of power.

Palmer is No 1 on the Senate ticket in Queensland, where the party’s following is strongest, but the UAP is also seen as a strong chance of picking up a Senate position in Western Australia and in New South Wales, where former One Nation senator Brian Burston leads the ticket.

A Newspoll published this week showed that, after a $30m advertising blitz, Palmer was recording between 5% and 14% of the primary vote in a host of marginal seats.

Liberal party state branches met last night to endorse the deal struck by the federal executive, with due diligence underway into candidates running under the UAP banner in all 151 lower house seats.

The prime minister, Scott Morrison, was asked on Tuesday to justify a potential preference deal with Palmer, who has previously compared Morrison to Heinrich Himmler.

“I did see some comments he made about an approach when we made a criticism some years ago,” Morrison said. “Look, I’m not going to be held back by that, nor am I here to offer any defences of Mr Palmer.

“He’s big enough to do that for himself. Parties will have discussions before close of nominations and the preference tickets, which will be issued next week in the normal course of events.”

Pre-polling for the election, where as much as 40% of voters are expected to cast their vote, begins on Monday when details of the preference arrangements will become clear.

While Palmer is unlikely to have sufficient volunteers to staff major pre-polling booths, there has been some speculation that Palmer may pay people to staff booths as he did at the 2013 election.

At that election, Palmer secured 5.49% of first preferences nationally, winning 11% of the vote in Queensland and 4.9% of the national Senate vote.

This saw Palmer elected as the MP for the seat of Fairfax, and two senators, Jacqui Lambie and Glenn Lazarus, elected. In 2014 at the rerun of the Senate election in WA in 2014, the party’s Zhenya Wang was also successfully elected.

Lambie and Lazarus quit the party in 2014 and 2015 respectively, and Palmer deregistered the Palmer United party in 2016.