Centre Alliance Senator Rex Patrick has thrown down the gauntlet to the cotton industry, challenging them to justify its use of water and its right to farm.

Sorry, this audio has expired Cotton production again under spotlight in wake of Royal Commission

Senator Patrick believes there should be a national debate and plans to introduce legislation next week which proposes a ban on cotton exports to get the conversation started.

"We live on the driest continent on the planet and yet we are using our precious national water resources to produce a water-intensive crop which we then simply export overseas such that foreign entities can profit," the South Australian Senator said.

"Twenty-seven percent of the entire allocation of irrigation water across the Murray-Darling goes to cotton. It's not in the national interest.

"We are quite literally sucking the lifeblood out the river system at the expense of downstream food producers, the towns and cities dependent on the river system for water supply, and the overall environmental health of the river system all the way to the Coorong lagoon in South Australia."

The Centre Alliance bill would amend the Export Control Act 1982 to make cotton a prohibited good, effectively killing a $2 billion-a-year industry in Australia.

Steve Whan, CEO of the National Irrigators' Council, said the proposal to prohibit a good that provided such a large percentage to an economy was ridiculous, and would likely send that economy into a depression.

Cotton Australia said a ban would achieve nothing.

"You could ban the growing of cotton tomorrow and exactly the same amount of water would still be used because it is allocated to the irrigator, or to the irrigation license, to be used as seen fit," said Michael Murray, Cotton Australia's general manager.

"It is perfectly legitimate for a society like Australia to have a discussion about how much water should be allocated to the environment and how much allocated for use.

"It's not legitimate to have an argument about what crops are grown. That's best left to the individuals to make those decisions."

Mr Patrick has visited Cubbie Station, the southern hemisphere's largest irrigator, which said last week it would not be planting a summer crop. ( ABC News: Dominique Schwartz )

It was a view shared by the Murray-Darling Basin Royal Commissioner Bret Walker.

Counsel assisting at the royal commission, Richard Beasley SC, said it was Commissioner Walker's view that if people or corporations were allocated water, they should be able to grow what they like with it.

"That's their business decision and risk," Mr Beasley told ABC Radio Adelaide.

"It would be a pretty strange system of government to start telling people what they can and can't grow.

"The real problem is how much water they're given in the first place."

Last week, Cotton Australia said all major cotton growing valleys in north-west NSW had no water allocated to them this harvest season.