It will take several billion dollars to save the Great Barrier Reef from water quality threats, a conservation group says.
WWF Australia has grave doubts the federal government will meet its current funding commitments to the reef, and even if it does the money won't come close to what's needed to save it from agricultural run-off and sediment build up.
WWF scientist and spokesman Sean Hoobin says a reef rescue plan, on the scale of the one forged for the Murray-Darling basin, is needed.
He expects a key scientific taskforce looking at reef health to recommend a multi-billion dollar investment when it reports back to government next month.
In the meantime, Mr Hoobin says federal Environment Minister Greg Hunt must keep his promise to provide $300 million by 2020 for critical reef health initiatives.
"When you look at the year-to-year budget allocations there is a $100 million shortfall," he told AAP on Tuesday.
"Next week's budget needs to address that. But our understanding is that it's going to be less than that."
Mr Hunt went to Cairns on Tuesday to announce $50 million in "new projects" to boost water quality, including efforts to keep fertilisers and pesticides off the reef.
In a morning interview on ABC radio he was asked if the money was, in fact, new but the minister didn't give a direct answer, instead describing it as "money which hasn't been assigned".
He also promised more funding for the reef in next week's budget but did not say how much, and said his government would "meet and beat" its existing commitments.
Mr Hoobin said a commitment on the scale of the Murray-Darling rescue plan was necessary if Australia was to meet its commitments to UNESCO, which will determine if the reef is listed as a World Heritage site in danger.
"And it's a much tougher budget circumstance than it was when the Murray-Darling plan was announced," he said.
Mr Hoobin said the taskforce due to report back next month included representatives from the federal government, and the scale of the investment its likely to recommend shouldn't shock anyone.
Greens Senator Larissa Waters accused the government of re-announcing existing funding, amid the reef's worst coral bleaching event on record.
She said the government recently approved Adani's $22 billion mega mine in Queensland's Galilee Basin in the full knowledge that the coal it produces will contribute to global warming and drive such bleaching events.
"We have viable renewable alternatives that don't sacrifice the 67,000 jobs the reef provides and that will generate thousands of new jobs," she said in a statement.