Australians will soon be eating genetically modified food whether they like it or not.

The nation's major grain handler, Graincorp, announced this week that genetically modified canola will be mixed in with the main crop in this year's harvest.

Anti-GM groups say the decision means canola oil and a large amount of commonly bought processed food made with canola will now be genetically modified.

They say staples that will become genetically modified include baby food, potato chips, biscuits, frozen vegetables, crackers and prepared meals.

They claim the move is premature because GM food has yet to be tested properly.

"All GM food has been created randomly. The DNA of these plants has been altered and no one really knows where it will go," said Madeleine Love, spokeswoman for Mothers Are Demystifying Genetic Engineering (MADGE).

"There have been no long-term studies on GM food to prove that it is safe."

Gene Ethics Network spokesman Bob Phelps said Australians had been deceived.

"Governments and the GM industry have been saying all along that they would segregate GM and non-GM canola and it's very clear that they lied to the public of Australia about this," Mr Phelps said.

"Now if we want any segregated non-GM canola, then of course we're going to have to pay extra for it."

Greenpeace has called on governments to label all GM food, including foods made with GM oils.

"People are having their choice cut off. It will become much harder and expensive to get hold of non-GM food," spokeswoman Michelle Sheather said.

"It's disappointing that while governments around the world are banning GM crops, in Australia we are rushing to plant GM canola.

"Consumers do not want to eat GM food. If our government and food regulator are serious about putting consumers interests first, they should agree to label oils and animal products for GM ingredients.

"The only way Australians will be able to avoid GM food is to avoid anything made with canola."

Graincorp corporate affairs manager David Ginn confirmed the two streams of canola will be mixed together this year after the October harvest.

Farmers who want their crops rated as non-GM will have to pay for extra testing.