Nobel prize-winning scientist Brian Schmidt issued that warning at the launch of the Physics Decadal Plan 2012-2021 at the Australian Academy of Science on Thursday.

The plan, drafted by a working group from the academy's national committee for physics, outlines a roadmap for the future of the science in Australia.

Professor Schmidt said physicists worked in a wide range of fields, including law, high-tech industries and finance. Without adequately trained physicists in the future, he said there would be less innovation and fewer new ideas to fuel the economy.

''It's a slow process and you just sort of wither away and find yourself 50 years down the road having an economy that looks like Greece does right now, rather than Germany,'' he said.

He said the average age of trained physics teachers was 60, and a third of physics students were being taught by teachers who were not qualified in the subject.

''You end up with fewer people being trained, and the ones who really are keen being under-trained for what their capabilities are,'' Professor Schmidt said.

The plan calls for secondary school physics teachers to be trained to a level three years' higher than the level they are to teach.

Working group convenor Professor David Jamieson said the opportunities from physics studies were not well promoted, and he called for targeted investment in physics education.