The world COVID pandemic and its economic aftershocks have triggered huge government recovery spending, according to a United Nations report - but less than a fifth of this will go toward climate change prevention.

"The world has so far fallen short of matching aspirations to build back better," said report author Brian O'Callaghan, who said governments were "trying to put out a house fire with a garden hose, while a perfectly good hydrant is available just next door."

The largest economies have plowed more than $14.5 trillion into pandemic-fighting efforts to date, with just $341 billion - or 2.4% - of that for green spending, according to the U.N.

"On the whole so far, global green spending does not match the severity (of the crisis)," wrote UNEP executive director Inger Andersen in the report.

While roughly 82% of spending is not green, an additional 3% is "dirty" according to O'Callaghan as it directly supports fossil fuel-heavy industries and companies.

The disparity in funding is most acute in Australia, the author said, where just $2.6 billion has been allocated for "green-oriented" spending. But there is still time to change.

The U.N. report advocates long-term spending on infrastructure and energy projects instead of quick relief schemes with an eye on immediate economic survival.

"Opportunities to spend wisely on recovery are not yet over (and) governments can use this moment to secure long-term economic, social and environmental prosperity," said O'Callaghan, who is also the lead researcher at Oxford University's Economic Recovery Project.

Worldwide, governments have put nearly $30 billion toward green research and development with another $55.6 billion going to reforestation and more than $66 billion spent on low carbon energy projects.

Scandinavian and central Europe countries including Norway, Finland, Denmark and Germany were among the only nations to devote around half or more of their recovery spending to environmental initiatives.