The South Australian Government will consider overturning a longstanding ban on genetically modified (GM) crops, after a review into the economic consequences of the policy.

Key points: A move to extend the GM crop moratorium until 2025 was resisted by grain growers

A move to extend the GM crop moratorium until 2025 was resisted by grain growers A review has found the ban has cost farmers $33 million since 2004

A review has found the ban has cost farmers $33 million since 2004 SA is the only mainland state that does not allow farmers to grow GM crops

The moratorium on GM crops has existed since 2004 and was due to expire later this year, but was extended until 2025 in a move that angered the SA grain industry's peak body.

South Australia is the only mainland state that does not allow GM crop cultivation.

A review prepared by University of Adelaide agricultural economist Kym Anderson said the ban had cost farmers more than $33 million from 2004 to 2018 and would cost them another $5 million over the next six years.

The report contains 19 findings and the SA Government said a majority of submissions, including those from groups representing SA farmers, "favour the immediate removal" of the moratorium on GM crop production and transport.

It proposed keeping Kangaroo Island as a GM-free zone in order to "retain access to Japan's high-priced market for GM-free grain".

Other key findings revealed there was no price premium for grain from South Australia given its GM-free status and the state's farmers did not "enjoy better access" to European Union markets.

Primary Industries Minister Tim Whetstone said the report "debunked myths" about the benefits of the ban.

"Investment in agricultural science has suffered under the moratorium, with the review finding the GM moratorium has discouraged both public and private investment in research and development in this state," Mr Whetstone said.

"The former Labor government continually spruiked the significant premiums for South Australia's non-GM canola.

"However the report debunks this view, finding there is no premium for SA grain when comparing data on prices of grain from neighbouring states."

Mr Whetstone said it was important to get feedback before a decision is made.

He said it was the start of "a journey for the consumer" to understand what a GM crop would mean for farmers who currently spend time and money on ground preparation, planting and chemicals.

"By and large it is taking away the opportunity that a farmer will need to be more competitive to be more productive," Mr Whetstone said.

The SA Liberals have long opposed the GM ban, and lobbied to have it overturned during their time in opposition.