The Federal Government has rejected suggestions its freeze on grants is pushing top researchers overseas to find work.

Treasury has frozen grants while Labor searches for budget savings to deliver its projected budget surplus.

Greens Senator Lee Rhiannon has told a Senate Estimates committee Australia could lose a generation of researchers as a result of the uncertainty.

She has rejected suggestions from Research Minister Chris Evans that her claims are outrageous.

"I would have though that a responsible government would be mindful of what's happened in the past, to learn from that to ensure that when you take such actions it doesn't play out in that way," she said.

But Senator Evans dismissed her concerns over the freeze.

"No-one apart from you is suggesting that it is playing out in that way," he said.

"I don't mean to be aggressive, but sometimes you make these statements and they're just plain wrong."

Senator Evans says the Government's mid-year budget update will reveal which grant programs it will cut.

"The way to think about it is there's a pause/freeze in place," he said.

"The government will make a decision about each program and there will be an announcement about whether the program is fully funded, partially funded or not funded and it will be obvious to the world then."