Prime Minister Tony Abbott has conceded he could lose in Monday’s party room vote, describing the Liberal leadership stoush as a “very chastening” experience.

Mr Abbott also said that how his frontbench MPs voted would be “entirely” up to them.

Liberal MPs and senators will meet at 9:00am (AEDT) on Monday to vote on a motion to spill the leadership, with Mr Abbott and deputy leader Julie Bishop so far declared to contest the positions they already hold.

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No other contender has yet emerged, though former leader Malcolm Turnbull was seen as the only real alternative prime minister.

Mr Abbott again warned his colleagues not to “look like the Labor Party” and “roll” a prime minister.

But when pressed, he conceded it “could” happen.

And as Mr Abbott worked to secure the numbers to defeat the spill motion and prevent a contest, he revealed a promise to wavering South Australian MPs that a competitive process would be held to build the nation’s next fleet of submarines.

In an exclusive interview with ABC political editor Chris Uhlmann, Mr Abbott said he had “always intended” to open up the bids to tender and denied it was a multi-billion-dollar bargain for party room votes.

“We are still a long way from doing this,” Mr Abbott said.

“The decision on this needs to be made by the end of the year at the latest, but nevertheless it is something which is still evolving, as you’d expect.”

But the matter warranted a personal call to SA Liberal senator Sean Edwards.

“The Prime Minister has called me and he has told me this and this is significant news,” Senator Edwards said on arrival in Canberra.

Abbott says spill motion a ‘chastening’ experience

Mr Abbott promised that if he held on to power, his Government would be “different and better this year than we were in every respect last year”.

“It’s a pretty chastening experience to have a spill motion moved on you after just 16 months in government – a very chastening experience,” he said.

“And I am determined that my Government, if it continues after tomorrow, will learn from this experience, will be different and better.”

The party room process will begin with a motion to open up or spill the leadership positions and the vote will be by secret ballot.

The ABC has been told that the Prime Minister’s office has put pressure on ministers to publicly back Mr Abbott, and so far about half of the 34 ministers and parliamentary secretaries have come out to say they would vote against the spill motion.

On Sunday evening Mr Abbott said: “It’s entirely up to ministers and parliamentary secretaries how they vote.

“It is a secret ballot. Now, I would expect that if a minister was incapable of supporting the Government, the minister in question would’ve spoken to me, and none of them have.

“But nevertheless this is an opportunity for people to do what they genuinely believe is right for the Government and for the country.”

-ABC