Public concern about environmental issues including climate change has slumped to a 20-year low since the financial crisis, a global study reveals.

Fewer people now consider issues such as CO2 emissions, air and water pollution, animal species loss, and water shortages to be “very serious” than at any time in the last two decades, according to the poll of 22,812 people in 22 countries including Britain and the US.

Despite years of studies showing the impact of global warming on the planet, only 49 per cent of people now consider climate change a very serious issue – far fewer than at the beginning of the worldwide financial crisis in 2009.

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Worries about climate change first dropped in industrialised nations but they have now also fallen in developing economies including Brazil and China, according to the survey by GlobeScan Radar.

The declining interest in climate change comes amid a backlash against costly green energy investments in an age of austerity. David Nussbaum, head of WWF UK, said “sustained pressure” was required from political leaders to combat climate change. He said it was only when “real indicators” of climate change came, such as floods and droughts, that public perceptions changed.

He told The Independent: “Of course people’s concerns about climate change changed in 2009 when economic pressures were rising… [But] the problems haven’t gone away… There are longer-term concerns that may not seem imminent that are extremely serious. A skilled political leader has got to grapple with how you act and respond to the immediate pressure people feel while helping [to take] account of the wider concerns and interests.”

Campaigners said the “perceived seriousness” of climate change had also fallen sharply since the unsuccessful UN Climate Change Summit in Copenhagen in December 2009. The summit ended in what was described as “confusion, disagreement and disarray” as political leaders failed to agree a legally binding deal to curb greenhouse gas emissions.

Graham Thompson, a spokesman for Greenpeace, said: “The public can see that the response of our politicians is completely inadequate to the threat scientists have revealed, and that dissonance is reflected in these polls.”

Doug Miller, chairman of GlobeScan, said: “Evidence of environmental damage is stronger than ever, but our data shows that economic crisis and a lack of political leadership mean that the public are starting to tune out.”

The Department of Energy and Climate Change reiterated the view of Ed Davey, Climate Change Secretary, that “the basic physics of climate change is irrefutable”.

The GlobeScan survey found that water pollution is viewed as the most serious environment problem worldwide with 58 per cent of people polled saying it represents a very serious concern.