Canberra - The Office of the Gene Technology Regulator said Thursday it has approved an application by Monsanto Co.'s Australian unit for the unrestricted commercial release of five genetically modified, or GM, herbicide tolerant and/or insect resistant cotton lines in northern areas.

The cultivation was restricted to southern areas due to uncertainty whether insect resistant GM cotton was more likely than non-GM cotton to become a weed north of 22 degrees south latitude, the office said.

Research demonstrated caterpillar pests aren't the major factor controlling cotton growth in northern areas, regulator Sue Meeks said in a statement.

The spread of cotton is mainly limited by the availability of water and nutrients and/or competition from other plants and insects such as grasshoppers, she said.

"Therefore, the genetic modification won't make these GM cotton lines weedy," she said.

The decision was made after comprehensive analysis of new research that addressed this issue and involved extensive consultation with the public, state, territory, federal and local governments and agencies.

Monsanto has indicated that large scale commercial production of these cotton lines isn't planned at this stage, and won't occur until a range of industry, community and infrastructure issues have been resolved, Meek said.