The South Australian Government will let mainland farmers grow genetically modified (GM) crops from the start of 2020, sidestepping State Parliament which has twice blocked the plan — and could do so a third time.

Key points: Mainland SA farmers will now be allowed to plant GM crops from January 1

Mainland SA farmers will now be allowed to plant GM crops from January 1 South Australian Parliament could block the plan for a third time but not until February

South Australian Parliament could block the plan for a third time but not until February Grain Producers SA have welcomed the decision by the government

New regulations allowing growers to plant GM crops from January 1 everywhere in the state except Kangaroo Island have today been introduced.

Parliament could still block these new regulations, but they will not have an opportunity to do so until sittings resume in February.

The new rules have the same effect as previous regulations that were struck down by the Labor Opposition and crossbenchers in Parliament.

A Government attempt to get a bill through Parliament to lift the GM moratorium also failed in the final sitting week this year.

Primary Industries Minister Tim Whetstone accused his parliamentary opponents of playing politics over the issue.

"When we first introduced regulations, the Labor Party and SA Best made the petty excuse that they didn't agree with the process and that legislation should be introduced," he said.

"The State Government did exactly that and inexplicably the Labor-SA Best alliance voted against the legislation to again show they are not the farmers' friend."

Decision is 'stupid in the extreme', Greens say

The Greens called Mr Whetstone's move "remarkable" and said it was very likely to backfire.

"Parliament twice in the last couple of months has said to the Government 'we don't want the moratorium lifted'," Greens MP Mark Parnell said.

"For the Government to come back with exactly the same model that was defeated twice before just strikes me as stupid in the extreme.

"Members of Parliament have said that they want to explore issues of contamination and issues of liability and the Government has just thumbed its nose at those MPs."

Overturning the ban on GM canola and other crops has been resisted, but is largely supported by farmers. ( Jessica Hayes )

However, growers have cautiously welcomed the Government's decision.

Grain Producers SA (GPSA) Chairman Wade Dabinett said farmers needed certainty.

"[We] can now continue putting plans and programs in place to understand what this means for SA so we can capture the opportunities we've been missing out on for 15 years," Mr Dabinett said.

Mr Dabinett said if the Government waited until February to reintroduce legislation, it'd be highly unlikely that farmers would be able to grow GM crops next year.

GM canola is usually planted between March and May.

"At the end of the day, the industry has been very clear, whether it's through legislation or regulations we want to have access to the technology," Mr Dabinett said.

"I think we've won the policy debate with the community."