South Australians will have to vote in a referendum when they go to the polls in March if the State Government gets its way.

The Government said the current electoral boundaries are unfair, with more people in some electorates than others, and it needed to change the constitution to fix the problem.

Attorney-General John Rau said the latest boundary re-draw meant the principle of "one vote, one value" no longer applied.

"If you're a South Australian and you're on the roll, your vote should be the same as anybody else's and I think most people, if they're asked that question, they'd give that answer," he said.

"This is not about Labor or Liberal. This is about whether a voter in one seat has a vote which is worth more than a voter in another seat."

For three of the past four elections, the Liberal Party has won the majority of votes, but not formed government, because the majority of its votes are concentrated in safe seats.

The Electoral Boundaries Commission recently re-drew the boundaries to keep in line with what's known as the "fairness" principle.

The result is that some Labor seats have now become nominally Liberal.

Shadow Attorney-General Vickie Chapman said the Government's call for a referendum is actually a bid to stay in power.

"Even Jay Weatherill [SA Premier] has said if you don't win, don't blame the system," she said.

"Clearly they've had this system the entire time of the office of this Government and this decision now to have a referendum is clearly just an act of a desperate Government to cling on to office.

"We have a system which confirms the principle of one vote one value so we don't need a referendum."

Experts say Labor would benefit

Political scientist Associate Professor Haydon Manning from Flinders University said the Electoral Boundaries Commission had remained within a 10 per cent leeway, which was allowed when looking at electorate populations.

He said the Government's proposed changes will benefit Labor.

"There's no doubt if we establish that a primary principle was one vote one value, that would benefit the Labor Party," he said.

"Previous Electoral Boundary Commissions have been very reluctant to play with that margin of plus or minus 10 per cent.

"They've tended to make sure the seats are about the average size. Going to the next election, they've used some of that latitude and that hasn't helped Labor."

The Government first needs to get its referendum proposal approved by Parliament.