Water Minister David Littleproud says he has not promised any more water to farmers, as part of a deal to pacify angry irrigators, while Nationals Party backbenchers suggest more reform may be needed.

Key points: The Federal Government has not promised irrigators extra water next year

The Federal Government has not promised irrigators extra water next year Some Nationals backbenchers want reforms to go further than an investigation

Some Nationals backbenchers want reforms to go further than an investigation Water Ministers in Victoria and SA have expressed concern at altering interstate water-sharing agreements

Mr Littleproud won the support of angry protestors who had been calling to "Can the Murray-Darling Basin Plan", when he committed to an investigation of how states share water, under the Murray-Darling Basin Agreement.

He wants Interim Inspector-General for the Murray-Darling Basin Mick Keelty to conduct the investigation by March 31, but needs the approval of state water ministers.

Mr Littleproud is also seeking the states' approval to ensure the Interim Inspector-General has appropriate powers and resources to investigate.

It is not clear what specific powers Mr Littleproud is seeking for the independent office.

At a media conference at Parliament House, Mr Littleproud was asked if he had promised any farmers extra water and he said "No".

Mr Littleproud was also asked if the Nationals Party room had considered draft legislation that would re-distribute water from the Commonwealth Environment Water Holder.

"I don't speculate on National Party room matters and it would be disappointing for any National Party member to leak outside the party room," Mr Littleproud said.

Backbenchers speak out

While Mr Littleproud won over the support of some protestors, Nationals backbenchers Damian Drum and Barnaby Joyce have suggested more reform may be needed.

"I've offered what I believe is something we should have a debate on, and that is the allocation of water from the Commonwealth Environment Water Holder to farmers for critical human and economic need, yes that will require legislation," Mr Joyce told RN Breakfast.

Rural news in your inbox? Subscribe for the national headlines of the day.

Mr Joyce, in his former role as Drought Envoy had previously suggested environment water be reallocated to farmers.

Many of the protestors — including farmers without enough access to, or priced out of, the water market — came from Mr Drum's Nicholls electorate.

"I don't believe you can have a worse plan [than the Murray-Darling Basin Plan] that is going to be more damaging to the agriculture sector than the current plan," Mr Drum said on Tuesday.

"Maybe it is time to have that conversation about [whether we have] taken too much water out of agriculture, for the environment — do we need to put some back?" he said.

Currently, federal legislation forbids the Commonwealth Environmental Water Holder from gifting water to other users.

"Water flowing out to sea" has become a symbol of water mis-management for the NSW Government. ( ABC News: Trent Murphy )

States jostle

Victorian Labor Water Minister Lisa Neville said her state would not support any changes to state water-sharing arrangements that negatively impact upon Victoria.

"While we agree the basin plan needs to be adaptive — these water-sharing rules pre-date the plan and are the basis for states making the best decisions possible for allocations to their farmers," Ms Neville said.

In a statement Ms Neville said she supported the establishment of the Inspector-General's office but would not support the office having the powers to change water-sharing rules, which pre-date the basin plan.

"If there are to be savings made by looking at transmission or other losses these should be looked at — but any additional water found in Victoria water needs to go back to our communities," the statement said.

New South Wales Deputy Premier John Barilaro has repeatedly threatened to withdraw from the Murray-Darling Basin Plan, and this week issued a set of demands, including to put a halt to water resource plans until the drought breaks.

Mr Barilarlo did not say if his proposals had the support of the NSW Cabinet.

South Australia's Liberal Party Water Minister David Speirs said his state would not agree to the "New South Wales National Party's latest irrational list of demands".

"We will not accept any less water flowing down the river and talk of removing the barrages at the Lower Lakes is nonsense that won't even deliver any water savings," Mr Speirs said.

Mr Speirs said he had advocated for the office of the Inspector-General.

"We are seeking further detail about the proposed review, however we would only be interested in looking at water-sharing changes that improved long-term outcomes for all jurisdictions," he said.

The water-sharing deal, known as the Murray-Darling Basin Agreement (not the Plan), mandates Victoria and NSW contribute a 50:50 share of the 1,850 billion litre yearly flow of water across the SA-Victorian border.

Interim Inspector-General Mick Keelty says he will look at the impact of current policies. ( ABC: Mark Moore )

Interim Inspector-General Mick Keelty said he would not exclude anything from consideration as part of his investigation.

"If there are problems I will turn a light on those problems, and I don't care whether it's the Murray-Darling Basin Plan or even some of the previous water-sharing arrangements," Mr Keelty said.

"I'll include everything and it may well make recommendations at the end of the review period for legislative amendment or for ministerial council to give consideration to different sorts of policies," he said.

"I can not pre-empt the outcome of the review but clearly there are a number of people who are not happy with current policies and I've been asked to look at those policies, look at the impact of those policies on water availability and report back, and that's what we'll do."

Water Ministers are expected to meet in Brisbane later this month.