The former Liberal prime minister told the National Press Club on Wednesday that he would “reserve his rights” to campaign against sitting government MPs or endorsed Coalition candidates, and he would keep his personal vote a secret.

Mr Turnbull in his NPC speech said Scott Morrison’s decision to cancel a $90 billion submarine deal with France was “blundering and deceitful” and accused Mr Morrison of hurting the nation’s relations with Europe.

The skewering speech came after months of other criticisms about the Prime Minister’s handling of climate change, the Covid-19 vaccine rollout, and the controversies around former minister Christian Porter.

Mr Turnbull refused to say on Wednesday that he would back the Liberal Party at the next election despite remaining a member of the party.

“It has been a long habit but it is also a secret ballot. That will be a matter between me and the ballot box,” he told the NPC on Wednesday.

“I haven‘t made a decision about (campaigning for independents). I remain a member of the Liberal Party. The independent I endorsed in the upper Hunter by-election was running against a National Party candidate and despite the indignation of Mr Barilaro, there is nothing in the Liberal Party rules that says you‘ve got to support the National Party.

“I will wait and see. I reserve my rights as they would say.”

In his speech on Wednesday, Mr Turnbull also revealed he has spoken to French president Emmanuel Macron since Australian-French relations soured over the cancellation of the Naval Group submarine deal in favour of UK and US nuclear submarines.

The former prime minister focused on Mr Morrison’s personal handling of the diplomatic controversy.

“Scott Morrison deliberately and elaborately set out to persuade the French that their deal was on foot and proceeding until he knew he had an alternative deal, where upon he dumped the French and his deceitful conduct was exposed,” Mr Turnbull told the NPC.

“I have spoken to Emmanuel Macron. He is a friend and I have stayed in touch with him since I left office.

“What Morrison has done, and he can blabber and people can spin it as much as they like, but this was a big double cross, deceitful conduct on any view, acting in bad faith.”