More than 300 protesters braved the Canberra cold on Thursday outside the Black Mountain buildings, many wearing white lab coats as a symbol of the scientific profession.

The federal government cut more than $100 million from the science body in May. The CSIRO Staff Association says the organisation is facing the largest staff reduction ever.

Angry staff members and their families joined the protest with signs stating slogans such as "clever country, dumb government" and "don’t send the CSIRO to the Abbottior".

Federal Labor science spokesman Kim Carr said the cuts would be crippling.

"The government is really doing great harm to Australia's national interest and are putting the nation at a disadvantage," Senator Carr said.

CSIRO Staff Association treasurer and scientist Scott Wilkinson said the Abbott government had broken a pre-budget promise that there would be no surprises in store for the CSIRO.

"Now we learn we have the worst surprise of all," he said. "The protest today is not about how the cuts are directly affecting us as workers at the CSIRO but about what it means for our nation. We believe these cuts are going to have huge reductions of the innovation and productivity of new ideas that this nation needs."

The CSIRO is responsible for such discoveries as Aerogard, a vaccine for Hendra virus and Wi-Fi.

Thursday's rally in Canberra was one of 14 around Australia, including in all capital cities.