The SA Government says it may be forced to sell off the state's Motor Vehicle Registry.

The current Liberal government says the former Labor administration struck a deal to sell the registry during a privatisation that left the Lands Titles Office in the hands of commercial consortium Land Services SA.

Treasurer Rob Lucas says the deal included Land Services SA paying $80 million for an “exclusive right” to negotiate for sell-offs including the Motor Vehicle Registry.

He said that if the current government does not go ahead with the privatisation, it would have to repay the $80 million with interest or give the consortium more control of lands titles services.

“If the repayment doesn't occur until 2020 then the repayment could be as much as $104 million,” he said.

Mr Lucas said Labor’s “secret deal” leaves the new Government “contractually bound” to at least undertake a scoping study into the privatisation of the agency.

“I've taken legal advice that we're now in this position,” he said.

“I can't rule out anything out because we haven't done the scoping study.

“If I was to rule something out at this stage, there may well be the opening for legal action against the Government on the basis that we've not gone into, as the contract requires us to do, reasonable endeavours to negotiate this particular deal.”

The former Labor government also privatised the Motor Accident Commission in a deal that Mr Lucas says Labor deliberately kept secret in the lead-up to the election.

Former treasurer Tom Koutsantonis said it was all above board.

“The consortium asked that we keep it confidential. We took advice and we agreed with them,” he said.

“Mr Lucas knows full well he doesn't have to go through with the deal. He can pocket the $80 million and just add seven years to the contract of the Lands Titles Office.”