Australians are donating less to non-government organisations, a study has found.

The study by the Australian National University's Development Policy Centre found in 2012/2013, Australians gave nine cents in every $100 to international development NGOs, compared to 14 cents in 2004 and 11 cents in 2007.

It said since about 2006, public giving in Australia to these organisations flatlined, just keeping up with inflation.

The research also found that although there has been an increase in the number of NGOs since 2008, more are sharing an essentially static pie.

Co-author of the report, Jonathan Pryke told Radio Australia's Pacific Beat program that even if individuals in Australia earn more, they tend to still donate the same amount as before.

"As Australians get richer over the last decade, their disposable income grows, whilst their giving to charitable organisations and development organisations remains the same," he said.

"So the proportion that they are giving decreases of what they can possibly give," he said.

Mr Pryke said higher performing aid organisations also received more donations and smaller ones often missed out.

"It creates a big risk that NGOs that charge ahead with their fundraising and who are thriving could be doing so at the expense of those who are struggling," he said.

But Mr Pryke said it was also important to acknowledge that Australia, over the past 15 years, had increased its donations by more than 140 per cent from $378 billion in 2000 to $920 billion.