In a wide-ranging opinion piece published by InDaily today, Speirs claimed that Tarzia “owes his position” to the Liberal Party Right and called on him to “resist” moving the party in that direction.

Speirs, who is currently in Scotland, resigned as Opposition leader two weeks ago saying he’d “had a gutful” of leaks and undermining.

The former leader said he was not offered a position in the new leader’s Shadow Cabinet but would have served on the frontbench “if asked”.

“Being outside the Shadow Cabinet will give me an independence of thinking and approach that will be uniquely freeing,” he said.

“I plan to engage broadly in areas of policy development that I have an interest in, and those that impact my electorate. I’m excited about this opportunity.”

Speirs wished Tarzia “all the best in his endeavours” but cautioned that “there is a mountain ahead for Mr Tarzia to ascend”.

“His team is confused and disoriented by the leadership change, and morale is low,” said Speirs, who added that leading a political party was “more than getting picked up by a chauffeur, popping on a bow tie and attending an endless array of alternate-drop meals at Adelaide Oval and the Convention Centre”.

“Political leadership is about a battle of ideas and bringing South Australians into relationship with a party that has clear values, a powerful policy platform, and a unified sense of purpose,” he said.

“I maintain that the house has been left in good order following the last two years of consistent work by a largely unified team, but it’s time for the rubber to hit the road: the election is on the horizon.

“I wish Mr Tarzia all the best in his endeavours. He thinks he can win the 2026 election. Many think he will be annihilated.

“I’ll watch with interest and contribute ideas from the sidelines.”

Speirs has previously refrained from commenting after Tarzia succeeded him in a ballot of Liberal Party MPs last week.

The former leader was a notable absence from Tarzia’s new shadow frontbench unveiled on Monday, fuelling continued speculation that he could follow through on his threat to resign the Liberal Party and move to the crossbench.

Read David Speirs’s full opinion piece here

But Speirs writes today that “I have a stake in the success of the Liberal Party”, adding: “My ongoing involvement will be key to the party maintaining at least the status quo at the next election.”

Speirs currently holds his southern suburbs seat of Black on a 2.8 per cent margin over Labor, which could be cut to 1 per cent under a draft proposal put forward by the Electoral Districts Boundaries Commission last week.

Political insiders and experts say Speirs carries a personal vote in Black and his resignation would give the Malinauskas Government a chance to take the seat.

David Speirs’ southern suburbs electorate could be cut to a one per cent margin under a boundary review. File photo: Tony Lewis/InDaily

Among the policy ideas floated by Speirs today are a cap on council rates – a policy the former Marshall Government could not get through parliament – and a “dramatic” reduction in public transport fares mirroring a 50c cap implemented by the Queensland Government.

He also said a new hospital in the Upper Spencer Gulf and a $125 million unmet needs program in mental health should be health policy planks.

But Speirs was sharply critical of a move to drop the “small and family business” portfolio from the shadow cabinet, which he held as leader.

That portfolio has been replaced with a “business and hospitality” portfolio held by Tarzia.

Speirs said: “We’re a small-business economy and these businesses need a party that has their backs.”

“That party should be unquestionably the Liberal Party. A Shadow Minister for Small and Family Business should be restored to Shadow Cabinet immediately. For a Liberal Party to abolish such a portfolio is breathtaking.”

Speirs also offered Tarzia some “unsolicited” advice on the direction of the Liberal Party, as an emboldened Right faction – spearheaded by right-wing senator Alex Antic – continues to consolidate and expand power within the Liberal Party’s internal machinery.

The former leader, who is factionally unaligned, said Tarzia must keep the party “centred” and avoid chasing “the latest fad emanating from the MAGA movement”.

“Tarzia owes his position to the Party’s Right grouping voting in an unusually disciplined block,” Speirs said.

“Consequently, there will be pressure on him to move the party in a more conservative direction. He should resist this.

“Elections in Australia (and even more so in South Australia) are won from the centre.

“Lurching to the right will please some of the lay party and a few parliamentarians, but it will deter large swathes of the electorate who will find culture wars distracting and far from a priority when they’re struggling to pay their mortgages.”

He also urged Tarzia to veto any move to relegate Jing Lee, the Liberal Party’s deputy leader in the Upper House, from a winnable spot on the party’s next Legislative Council ticket.

InDaily has previously reported that the Right has its eyes on dumping the moderate MP and could wield its increasing numbers on State Council to make that happen.

“Jing is a brilliant contributor who has unparalleled networks with South Australia’s multicultural communities,” Speirs said.

“Demoting her would send a cruel signal to these groups and undo years of hard work.

“Mr Tarzia should tell Jing’s detractors to back off and insist she be preselected in one of the top three winnable spots – ideally in the top spot, given her seniority in the leadership team.”

Speirs addressing a press conference shortly after taking the leadership in April 2022 with Jing Lee (right) behind him. Photo: Tony Lewis/InDaily

Speirs also urged the party to open preselections in marginal seats “immediately” but warned it would be “challenging to recruit candidates after a leadership change”.

“Mr Tarzia will have to work hard to convince prospects that they will be supported and have a decent chance of success,” he said.

InDaily sent a list of statements from Speirs’s opinion piece to Tarzia’s office.

In a statement, Tarzia said: “My team is focused on the issues we know are important to South Australians: the cost of living, housing and health.

“We have a strong, capable team that is passionate about improving the lives of all South Australians,” he said.

“I have personally taken on the portfolios of business and hospitality, because small business is the critical backbone of South Australia’s economy and the Government must do more to address the challenges they currently face.”