An independent group of scientists say the Federal Government should scrap the draft Murray-Darling Basin plan, which they say "manipulated science" in an "attempt to engineer a predetermined political outcome".

The Wentworth Group of Concerned Scientists says the plan does not provide enough information on how much water is needed to return the basin to health and does not prepare for the effects of climate change and future droughts.

The group has spent two months analysing the draft, which drew criticism from environmentalists and farmers alike when it was released in November.

Environmental engineer Tim Stubbs says it beggars belief that the Murray-Darling Basin Authority (MDBA) would recommend spending $9 billion to buy 2,750 gigalitres of water at the same time as proposing an increase in groundwater extractions of 2,600 gigalitres.

"We've actually said the Government should withdraw the draft plan," he said.

"The primary reason for that is the draft plan does not provide the information that anybody needs, whether it be a politician, the Government, the Parliament, an irrigator, an environmental scientist.

"It doesn't tell us if we get a healthy Murray-Darling Basin. Clearly we don't. They make it clear they don't achieve all the objectives that they set out to achieve.

"The plan should clearly say which ones we don't. Are we going to achieve our objectives? Are we going to have a healthy estuary? Are we going to have an open Murray mouth that is leading to a health estuary?"

Unknowns

Mr Stubbs says the figure of 2,750 gigalitres to save the system was decided before the plan was begun.

"The authority decided on a number in March last year. The science has then subsequently been done and generated that number at the end of the process," he said.

"It's difficult to see if we've got the full picture yet. We've been provided a picture in the draft plan that says 2,750 [gigalitres] is the best volume for the basin.

"The number in the plan doesn't tell us how the export of salt will happen. We need to export about 2 million tonnes of salt annually.

"The plan also doesn't clearly address how increasing groundwater extractions by 2,600 gigalitres will impact the surface water.

"There's a whole lot of unknowns that surround that 2,750 number."

Mr Stubbs says water buybacks and infrastructure grants should cease until the plan is improved.

"There is enough good work that the authority has done, good modelling tools that they've developed, good work on the social and economic side of the analysis that can actually be brought together to provide a plan that lets people understand the environmental outcomes," he said.

The Wentworth Group is an independent body made up of economists and scientists, including former Australian of the Year Professor Tim Flannery.

The Wilderness Society's Chris Daley agrees the plan must be rewritten.

"Our position is quite clear, that Tony Burke should be sending that back to the Murray Darling Basin Authority to say that this isn't a plan that's going to save the river," he said.

"In it's current form it's a plan that's going to waste $10 billion of taxpayer's money, and it's not going to achieve the outcomes they desire or meet the legal requirements of the Water Act."