Cory Bernardi has warned the Turnbull Government not to count on his vote even for coalition policies the renegade Liberal senator backed at a federal election seven months ago.

While he pledged his support for money bills to keep the Government operating, Bernardi hinted he wouldn't rubber stamp other legislation. As expected, the South Australian used the first sitting day of the year to inform Parliament he had resigned from the Liberal Party to guide his political movement, the Australian Conservatives.

His defection means the Turnbull Government will need the support of nine of the 10 independent cross benchers to have its legislation clear the Senate against opposition from Labor and the Greens.

Bernardi defended the "difficult" decision, arguing the political class was out of touch. He warned that Australia was succumbing to the lure of personality politics which he claimed was shrinking the debate and compromising the sense and values of the many.


"I stand here today, both reluctant and relieved," he told the Senate hours after informing Prime Minister Malcolm Turnbull of his decision. "Reluctant because this decision has weighed heavy on my heart, but relieved because whilst it is difficult, I believe it is the right thing to do."

Bernardi criticised policies the Government took to the election that affected the ability of Australians to plan for their retirement, insisting it diminished faith and confidence.

"The Government is living out of its means and the community and our children are paying the price," he told reporters.

"I am not prepared to do nothing or maintain the status quo while we rack up billions in debt."

Attorney-General George Brandis led the coalition attack on Bernardi, labelling the defection a betrayal of conservative values. He reminded him that he had been elected by South Australian voters as a Liberal and noted that in the time since then the Government had changed none of its policies.

"If one seeks to restore confidence in the political class, it is a poor way to begin by breaking the promise one makes to one's electors to serve for the political party on whose platform and whose ticket one stood," Brandis told Parliament.

Brandis said the Government expected him to continue supporting government policies given they were what he stood for when elected.

Earlier Turnbull told a meeting of Liberal and Nationals MPs that the honourable course would have been for Bernardi to quit Parliament.

Bernardi cited the toppling of Tony Abbott as Prime Minister in 2015 as a reason for his defection, insisting politics was broken and voters were looking for alternatives outside the major parties.

Abbott, in a none-too-subtle dig at Turnbull, said while "Cory and I have sometimes disagreed, I'm disappointed that more effort has not been made to keep our party united".

Labor said the "extraordinary" defection was a consequence of the Prime Minister's failure of leadership, and showed the Government was bitterly divided.