Liberal Party elders have condemned Tony Abbott’s role in bringing down the Turnbull government, saying the former prime minister’s behaviour has been “lamentable”.

Conservative supporters of Mr Abbott have also told the ABC’s Four Corners that he had “unfinished business” and he actively contributed to the volatility in the Liberal Party.

Meanwhile, Mr Abbott has declared the “era of the political assassination is over” in the wake of last week’s leadership spills.

On Monday, Mr Abbott used a radio interview with Ray Hadley, on Sydney’s 2GB, to say he thought Australia was better for Scott Morrison becoming Prime Minister.

“A lot’s happened, but I think our country is in better shape today than it was a fortnight ago,” he said.

“The era of the political assassin is over, and thank god for that.

But former foreign affairs minister Alexander Downer said the Liberal Party has been wracked by bitterness since Mr Turnbull rolled Mr Abbott as prime minister.

“That, in turn, can lead to acts of attempted revenge,” he said.

Mr Downer said Mr Turnbull was right to exclude Mr Abbott from the frontbench after the 2015 leadership spill – a move some say further contributed to the party turmoil.

“I don’t think Tony Abbott’s mindset was the mindset of playing in the team led by Malcolm Turnbull, in all honesty,” Mr Downer said.

“So I’m not sure that it was a mistake to exclude him from the cabinet.”

Mr Abbott famously pledged not to wreck, undermine or snipe against Mr Turnbull. But former Liberal Party treasurer Michael Yabsley has told Four Corners Mr Abbott did just that.

“What Tony has done is really regrettable, lamentable. Tony made something of a statesman-like speech when Malcolm defeated him for the leadership … He has not delivered on that,” he said.

“On the contrary, he has destabilised. He has really done everything he could to make things as difficult as possible for Malcolm Turnbull.”

Supporter says Abbott ‘maintained agitation’

Conservative Liberal MP Concetta Fierravanti-Wells, a signatory to last week’s petition that would essentially dethrone Mr Turnbull, said Mr Abbott has maintained his anger on the leadership loss.

“For Tony, this is unfinished business and he’s got his agenda,” she said.

“Certainly Tony has contributed to a degree of intense debate, if I can put it in those terms. But it’s a much more volatile political situation than it used to be, and certainly Tony has very effectively appealed to the conservative base of the Liberal Party.

“I’m not apportioning blame either way, I think that there is a sense by some in the party that there is unfinished business, and this is now manifesting itself in the degree of instability that we are now seeing.”

Liberal Party president Nick Greiner was also critical of the former leader’s behaviour.

“He chose not to leave, which, of course, I – and most people – think previous prime ministers ought to do. He chose not to do that,” he said.

“He’s obviously behaved in the way that everyone in Australia can see, and he’s had some help from a few reasonably rabid members of your profession [the media].”

Mr Greiner also criticised sections of the media and the party for working against Mr Turnbull.

“There would appear to have been a considered long-term campaign,” he said.

“There’s been a concerted co-ordinated campaign between a very, very small number of members of the federal parliamentary Liberal Party and, frankly, a pretty small number of media that are concentrated in a handful of outlets or newspapers.

“In my 30 or 40 years in public life, I don’t remember a more blatant media campaign.

“That’s I think one of the distinguishing features of this period is that the media, or substantial elements probably of the media, have chosen not to just comment on the usual argy bargy of politics, but have actually been active participants in a campaign against the prime minister.”

Mr Abbott is considering accepting an offer to take up the role of special envoy to the Prime Minister in indigenous affairs in the new Morrison cabinet.

“What I’d like to know from Scott is exactly what he has in mind,” he told Hadley on Monday.

“I want to see us making a difference here … I don’t just want a title without a role.”

Hadley urged Mr Abbott to take on the job, saying the former PM had a contribution to make.

“Please… take on this role, we need your experience and your expertise,” he said.

-with agencies