Leading medical researchers are concerned that rumoured plans to slash funding to the sector in the next federal budget will send researchers offshore.

Professor Doug Hilton, director of the Walter and Eliza Hall Institute (WEHI) in Melbourne, says it is impossible to say for sure how big the cuts to the National Health and Medical Research Council (NHMRC) will be.

But information leaked to a number of senior researchers suggests the cuts could be as high as $400 million during the next three years.

"I think there's a sentiment in government that somehow medical research has been dining out for 10 years, has been doing exceptionally well, and that it's time we felt some pain," Professor Hilton said.

"The cost of doing research is going up and up. It's taken us 10 years to get to the point where we are somewhat competitive internationally.

"Anything other than maintaining the budget in real terms would be disastrous."

Professor Hilton says the cuts probably will not target any particular research field, but will make things difficult across the board.

"We hope they're not floating the $400 million [figure] so they can it then cut by $200 million and tell us how lucky we are," he said.

He says many senior investigators with a long research track record have long-term funding in place, and will be immune to the cuts.

"The people that are going to feel the pain are the young investigators getting into the industry, the smart young kids at university," he said.

Professor Hilton says there are a number of programs that would be difficult to fund without the current NHMRC budget.

"For example, testing new pharmaceuticals that we know to be effective against one type of cancer and trying to work out the combinations that will make them effective for treating lung cancer or ovarian cancer," he said.

Professor Julie Campbell, president of the Association of Australian Medical Research Institutes, told the ABC's Health Report that the cuts would amount to about 19 per cent of the budget.

"It'd be absolutely disastrous to the health and medical research community," she said.

"Already with the NHMRC there is only a 23 per cent success rate, so 77 per cent of grant applications do not get funded - even though about 70 per cent are deemed that they should be funded."

Professor Hilton says the rumoured cuts would be a huge step backwards.

"We have a vibrant sector, we're attractive to people overseas, there's a brain gain," he said.

"We've worked so hard as a sector, with the support of government, to create centres of medical research in Australia that are a magnet for people overseas.

"To think that can be turned on and off like a tap without consequences is just naive. If the money dries up they'll go overseas."

A spokeswoman for the Minister for Mental Health and Ageing, Mark Butler, refused to confirm whether there would be cuts to the NHMRC budget.

"Funding for the NHMRC will be considered in the context of the 2011 budget," she said.