PETER VAN ONSELEN: Why bitter ex-PM Malcolm Turnbull is so out to get Peter Dutton - as his brutal comments about the Opposition Leader stun

Former Liberal PM Malcolm Turnbull has once again taken aim at current Liberal leader Peter Dutton.

I am starting to wonder if Turnbull will ever have anything nice to say about anyone involved in the party that helped him achieve his life's ambition of becoming PM.

He's described Dutton as 'a thug', claiming that his approach to politics is all about stoking 'division and animosity'.

It is the ultimate case of the pot calling the kettle black - given Turnbull's track-record.  

Malcolm Turnbull is the last major figure left from that bitter period in Australian politics still waging war over his perceived wrongs of the past. 

Kevin Rudd, Julia Gillard and Tony Abbott have all moved on. Not Malcolm Turnbull. He's happy to play the role of Liberal critic whenever needed.

Try as I might I cannot think of a more divisive figure within the Liberal Party over the past 20 years than Malcolm Turnbull.

While Turnbull has labelled Dutton a thug, the bigger political thug in recent times would surely have to be Turnbull. His political career was defined by stepping over others. 

I'm not just talking about his quiet, ruthless campaign against Tony Abbott. The history of Turnbull's naked political ambitions go much further back.

He entered parliament at the 2004 election - taking out one-term Liberal MP Peter King - and quickly worked his way into John Howard's cabinet.

All of a sudden that cabinet started leaking for the first time in a decade. He denied being responsible. Perhaps it was a coincidence.  

When Howard's leadership came under pressure in the countdown to the 2007 election, Peter Costello was the alternative to lead in most people's minds. Turnbull suggested himself.

After the election defeat Turnbull nominated for the Opposition leadership, only to lose to Brendan Nelson. 

He marched into his new leader's office to give him a serve, before challenging for the leadership within the year.

Dr Nelson claimed Turnbull constantly made 'life difficult' for him for his nine months in charge, before he finally seized the job himself. 

After Tony Abbott secured a thumping 2013 election win he fought a war on two fronts - against the newly minted Labor opposition and Team Turnbull.

Eventually Turnbull orchestrated a coup and took over, only to lead the Coalition to a disastrous 2016 election 'win' - securing the most slender majority possible - 76 seats in the 150 seat House of Representatives. 

By all accounts it was a disastrous campaign and Turnbull was a difficult political leader to manage on the campaign trail.

While Turnbull's career in politics was punctuated by forceful political moves to seize power off internal rivals, his animosity towards others came later. 

His behaviour since his forced retirement is a far cry from Julia Gillard's dignified post-politics career. Turnbull never got over being ousted from the prime ministership. 

Not one to break bread thereafter, he has fought a public relations war ever since against everyone and anyone he believes conspired against him.

This is where we get to what is really behind his criticisms of Dutton.

In 2018 Dutton decided - rightly or wrongly - that he would challenge Turnbull for the leadership. 

It was an ambitious move Turnbull must have understood, given he'd done the exact same thing to Abbott in the Coalition's first two years in office.

I was critical of Dutton's move against Turnbull at the time, taking the view that after so many years of leadership instability on both sides it was time for the Liberal Party to pick and stick, no matter the electoral consequences. To show that it was putting those years behind it.

In the aftermath of the Dutton-Turnbull showdown Scott Morrison came through the middle and took over as PM, going on to win the seemingly unwinnable 2019 election.

Turnbull retired, Dutton's political career continued. But Turnbull's animosity grew like a cancer. Dutton's role as ringleader for the putsch was not been forgotten.

So it is no surprise that he makes regular appearances spitting bile in the Opposition Leader's direction. 

Apart from the unhealthy nature of being consumed by such bitterness I can actually understand why Turnbull feels the way that he does. 

Having the prime ministership wrestled away from you must be a devastating blow.

But let's not kid ourselves that Turnbull's critique of Dutton is motivated by anything other than spite. 

Nor that he is a pillar of virtue when it comes to rising above political thuggery, divisiveness and shows of animosity.

Then there is his suggestion that Australians should be terrified of the prospect of Dutton the politician.

Turnbull promoted Dutton within cabinet and considered him a key political adviser in his team.

If Dutton were really as bad as Turnbull now claims, what does it say about the former PM's preparedness to promote and support such a person?

But we've heard these attacks before. While the TV hosts and their audience last night were shocked to hear Turnbull's attacks, anyone keeping a close eye on politics in this country wouldn't have been.

Turnbull made similar observations on the ABC series dissecting the Coalition's time in power, also describing Dutton as a thug.

His attacks on Dutton are becoming so predictable I doubt they shift a single vote against the Opposition Leader. 

They may even help Dutton within the mainstream, where Turnbull never managed to be seen as anything other than out of touch.

His attacks say more about him than Dutton.

I was a strong supporter of Malcolm Turnbull's political ambitions. I was one of his preselectors back in 2003. I advocated for him to assume the opposition leadership. 

For him to take over the prime ministership. I hoped he would elevate the moderate cause within the Liberal Party. I opposed the move by Dutton to replace him.

And he's good company: quick-witted, amusing with his storytelling and armed with a wealth of facts and anecdotes at his fingertips.

But fast forward to today, it is with a heavy heart that I have to admit that on reflection he's been a net negative for the Liberal Party and a disappointment to small L liberals.

Now, at nearly 70-years of age, Turnbull would rather settle petty personal grudges than act with the sort of post-parliamentary career dignity befitting a former PM.

It's a crying shame. Mostly for Malcolm.