Mr Littleproud, who also holds the water portfolio, said on Tuesday he wasn't sure if climate change was man-made, but he has repeatedly acknowledged it's happening.

"I am not a scientist. I haven't made an opinion one way or the other, but I don't think it really matters," he told Sky News.

Mr Fitzgibbon attacked the coalition for lacking a comprehensive drought plan or strategy since coming to power in 2013.

"The problem is, as demonstrated yesterday, it turns out the drought minister is also a climate change denier. It's not a very good start," he told ABC Radio National on Wednesday.

Labor wants more focus on drought mitigation through addressing climate change and adapting to new farming methods in the face of more prolonged droughts.

Mr Fitzgibbon said Prime Minister Scott Morrison wasn't doing enough for drought-affected farmers.

"The farmers have become Scott Morrison's forgotten people," he said.

"No real action on his part despite the fact that it's very, very clear based on all the advice that this thing is not going to get better any time soon."

Mr Morrison has made tackling the drought a high priority since taking over the top job last year, with a future fund to dole out $100 million a year for projects from next year at the centrepiece of his efforts.

Water policy has become increasingly vexed as farmers contend with the ramifications of drought across swathes of eastern Australia.

The Greens want the federal government to slap a moratorium on non-water users buying the precious commodity while the Murray-Darling Basin remains in "crisis".

South Australian Greens senator Sarah Hanson-Young is expected to move a motion in the upper house on Wednesday noting market exploitation by water barons and corporate irrigators hurting family farms.

Australian Associated Press