A former South Australian Liberal senator who lost his seat at the last federal election has accused SA senator Cory Bernardi of misleading the party's preselectors.

Sean Edwards was fifth on the party's Senate ticket and would have retained his seat if Senator Bernardi had not run for the Liberal Party in 2016.

Senator Bernardi on Tuesday quit the Liberal Party to establish his own party, the Australian Conservative Party.

"It's a gross misrepresentation. He has misled the preselectors of the Liberal Party and indeed the voters," Mr Edwards said.

"He talks about principled policy making. I would expect that he would adhere to those things and answer questions when they're posed to him in a principled way."

Just more than 2,000, or 0.19 per cent of South Australians, gave Senator Bernardi their first preference, whereas 31.05 per cent voted for the Liberal Party as their number one pick in the Senate.

Mr Edwards said the Senator was going against the electorate's wishes.

"Now we have yet another Senator on the crossbench who has set up a political party who will spend all of their time electioneering effectively rather than worrying about what they were elected to do," he said.

Bernardi's exit reflects 'divisions' in SA Liberal Party

Senator Bernardi cited a clash of ideas between conservative and moderate Liberals as his reason for leaving.

In a speech to Senate colleagues in Canberra on Tuesday, he said the "level of public disenchantment with the major parties" and lack of confidence in political processes was "very, very strong".

But SA Premier Jay Weatherill said Senator Bernardi's exit was reflective of deep and long-standing divisions in the state's Liberal Party.

"The divisions and disunities that exist in the South Australian branch of the Liberal Party are historic," he said.

"They go back for generations and they continue to manifest themselves today."

Mr Weatherill used the example of former Liberal leader Martin Hamilton-Smith who left the party for a ministerial position in Labor's Cabinet.

"Martin Hamilton-Smith was about the only Liberal that ever came up with a policy idea and when he tried to promote them inside the Liberal Party he couldn't get any support," he said.

"They've got no mechanism for managing disagreement about who should get what position.

"They've got no mechanism for managing disagreement about policy."

Mr Weatherill said he would not negotiate with Senator Bernardi's new party if it ran candidates in next year's state election.

SA Liberal defector 'understands' Bernardi's position

Martin Hamilton-Smith said he understood "where Cory Bernardi is coming from".

"I was a non-aligned conservative in the Liberal Party when I was member of it," he said.

"He will be abused, he'll be called a rat, he'll be called a traitor, he'll be enduring the same sort of abuse that was thrown at me.

"But I, in my time in the Liberal party, no doubt like Cory, saw quite a bit of rat behaviour and treachery inside the tent.

"I've chosen a different pathway to Cory but there's a message here for the Liberal Party."

Mr Hamilton-Smith said the Liberal party wanted politics in Australia to be "a meal that is only two courses", but that "this is democracy working and the people are sending a very clear message — business as usual in state and national politics is over".

Then-liberal Martin Hamilton-Smith (L) defected to Jay Weatherill's Labor government in 2014. ( ABC News )

"I believe in supporting the Government of the day. I've enjoyed doing that, I've found it really constructive," Mr Hamilton-Smith said.

"People are sick of all the spin and all the nonsense from the political class. They want some straight talking, plain speaking answers to their issues, not the fringe issues that don't really matter to them."

He would not comment on whether he had spoken to Senator Bernardi.

This is 'rebel action', SA Liberal leader says

SA Opposition Leader Steven Marshall has denied there is division in the party at a state level.

"These are rebel actions by Martin Hamilton-Smith and Cory Bernardi," Mr Marshall said.

"The state team is 100 per cent united. There will be no defection from the state team."

Mr Marshall said his party had an effective methodology to manage differences.

"The Liberal Party is the natural home for both the Liberal people within our society and the conservatives," he said.

"We manage those disagreements in our partyroom."

Mr Marshall said Senator Bernardi had indicated he would not run candidates at the next state election.