Deputy Prime Minister and Nationals leader Barnaby Joyce said on Thursday it was evident the Turnbull government's honeymoon was over and unity was vital.

A colleague of Mr Abbott's said he believed the former prime minister had given up on returning to the top job and was now motivated by making life uncomfortable for Mr Turnbull, as well as protecting his own legacy.

Mr Abbott's interventions this week – on tax cuts and the submarine contract – have clouded the government's attempts to take on Labor over tax policy. It has also frustrated the Liberal Party machine, which is trying to establish election themes. Mr Turnbull has been trying to run a line that Labor's tax policies pose a threat to the economy transitioning away from the mining boom.

Relationship nadir

On Tuesday, Mr Abbott dared Mr Turnbull and Treasurer Scott Morrison to fund their planned income tax cuts though budget savings, not tax increases. In doing so, he stood by his notorious 2014 budget and its tough spending cuts, many of which were abandoned or blocked.

Senior sources countered, noting Mr Abbott had funded his tax cuts, such as the abolition of the carbon tax, with $20 billion in tax increases, including the deficit levy and the re-indexation of fuel excise.

On Wednesday, the relationship between Mr Abbott and Mr Turnbull reached a nadir when Mr Turnbull called in the Australian Federal Police over a leak to The Australian Newspaper which painted the Prime Minister as weak on national security.

The article by the paper's foreign editor Greg Sheridan, who is a close friend of Mr Abbott, reported that a draft defence white paper produced under Mr Abbott would have seen the 12 submarines, to be commissioned by the government, built earlier than Mr Turnbull was now proposing. Mr Turnbull and defence force chiefs rejected this and said Mr Abbott was advised to the contrary when he was prime minister.

Mr Abbott denied he leaked the draft white paper. His friend and ally, Eric Abetz, suggested on Thursday that the culprit could have been a staffer or official.