Federal Labor has signalled it will withdraw support for a major part of Murray-Darling Basin Plan, if elected.

Key points: Labor to repeal cap on buying more environmental water

Labor to repeal cap on buying more environmental water Labor to scrap compliance role of basin authority

Labor to scrap compliance role of basin authority Government says Labor plan is a hoax

Opposition Water spokesman Tony Burke has announced Labor would change the way 450 gigalitres of water is recovered, by "restoring the socio-economic definition" for delivering water.

It comes less than a year after the Government and basin states agreed on a way to measure the socio-economic impact of recovering water.

Making the announcement with the South Australian state Labor Opposition in Adelaide, Mr Burke said Labor would also call an urgent review of the impact of climate change across the Basin.

It would also "urgently renegotiate the Menindee agreement, which determines how the lakes are managed".

Mr Burke has already committed to repeal a cap on buying more water from farmers to return to the environment, and remove the compliance function of the Murray-Darling Basin Authority to a newly established federal Environmental Protection Agency.

Water Minister David Littleproud described Labor's plan as a "hoax".

"Labor can't change the neutrality test unless all of the states agree and they know it," Mr Littleproud said.

"The plan is locked and no one should be playing politics with it."

Irrigators say it's difficult to get states to agree

The National Irrigators' Council chief executive Steve Whan said his group did not support the proposal.

"The 1,500 gigalitre cap (on buying more water from farmers) was actually introduced with Labor's support," Mr Whan said.

"I think one of the fundamental things we need to see out of the coming few months in the lead up to the election in May is that we keep the basic bipartisanship on the plan," NIC chief executive Steve Whan said.

Mr Whan believed it would be difficult for Labor to get the states to agree to any change.

"If they can't get the states to agree to that change then they're at an impasse which will effectively cease further action unless the Commonwealth Government wants to go it alone which would be quite difficult."