Australian Conservatives defector Dennis Hood has fired a parting shot at Cory Bernardi's fledgling party, suggesting it is destined to have "no impact" in state politics.

SA Premier Steven Marshall on Monday revealed Mr Hood — a South Australian Upper House MP — would join the Liberals, bolstering the party's numbers in the Legislative Council.

Mr Hood was the Australian Conservatives' parliamentary leader in SA, and was likely to be its only member, with Robert Brokenshire set to lose his seat.

Cory Bernardi's Australian Conservatives are now unlikely to be represented in SA's Parliament. ( ABC News: Nick Haggarty )

Both joined the Conservatives when it amalgamated with Family First last year, following Senator Bernardi's own defection from the Liberals.

Mr Hood's surprise move was revealed at the first Liberal partyroom meeting since the state election, when the Conservatives failed to win a seat despite running 33 Lower House candidates.

He said the party is primarily interested in federal issues.

"They received just over 3 per cent of the first preference votes in the Lower House which is not going to get anyone anywhere," he said.

"If you want to stay with something that's heading down that path then pretty soon you'll find that they have no members in Parliament and really no impact."

Dennis Hood was elected to Parliament in 2006 representing Family First. ( ABC News )

He denied he acted out of self-interest and praised the Liberals' policy agenda, including plans to cut payroll tax.

"The truth is, this government is a brand new government. It's been in place for just one week. It has a terrific vision, a vision which I completely endorse for this state … the overlap is very substantial," he said.

Mr Hood was elected to SA Parliament's Legislative Council in 2006 representing Family First and his move has been approved by the Liberal partyroom.

At the meeting, Mr Marshall was also re-endorsed as the party's leader and, by extension, the state's Premier.

Senator Bernardi has expressed disappointment at Mr Hood's decision, saying the MP did not contact him directly to let him know of his plans.

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"I found out this morning. I received a text message from a friend of mine in the Liberal Party who informed me of it and I then had a conversation with Dennis," Senator Bernardi said.

"It is what it is and I can't change it and you know I've learnt in life you react to things you can control. If I can't control other people's actions then it's a matter for them."

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In a separate video response posted on Twitter, Senator Bernardi delivered a message to Australian Conservatives' supporters and members.

"We're going to continue to pursue our principled approach to politics come hell or high water," he said.

"Stick with us, we will achieve our goals. We just need to have the resolve to see them through to completion."

It is not the first time the Australian Conservatives have been dealt a parliamentary blow.

Former Family First candidate Lucy Gichuhi chose not to join Senator Bernardi's party when she entered the Senate last year.

Senator Gichuhi subsequently joined Prime Minister Malcolm Turnbull's Liberal party room.

11 new faces in Liberal party room

Before announcing the move, Mr Marshall received a standing ovation as he entered the meeting in the Old Chamber.

There were 11 new faces among the 33 members of the Liberal party room, including four MPs who successfully claimed seats from the Labor Party.

Treasurer Rob Lucas was elected Leader of the Government in the Legislative Council, taking over from Tourism and Trade Minister David Ridgway.

Robert Brokenshire with Australian Conservatives leader Cory Bernardi. ( ABC News: Tom Fedorowytsch )

Hartley MP Vincent Tarzia has been nominated Speaker, while Andrew McLachlan is set to rise to the Presidency of the Legislative Council.

Those appointments will need to be confirmed by Parliament.

Mr Hood's defection will make little difference on the floor of the Parliament, given Mr Hood mostly voted with the Liberals, and Mr Marshall will still need to convince SA Best, the Greens or Labor to pass controversial legislation.

But it is a major blow for Senator Bernardi's plans to turn the Conservatives into a significant player in Australian politics.

The Australian Conservatives have already removed Mr Hood's name from the team list on its website.