
Teenage climate activist Greta Thunberg said her demand at Davos that world leaders immediately stop investing in fossil fuels had been 'completely ignored' after she was branded 'a joke' by the US treasury secretary.

The 17-year-old Swede, speaking at a Fridays for Future protest in the Swiss Alpine town, said she was 'expecting no less' from the nearly 3,000 business and political delegates at the World Economic Forum.

In her speech at Davos, she told the world's media that 'our house is still on fire and your inaction is fuelling the flames' before asking: 'What will you tell your children was the reason to fail?'

Those remarks earned her a rebuke from US Secretary Steven Mnuchin who told her to 'study economics' then 'come back and explain it to us.'

Greta Thunberg (centre) has told protesters during a Fridays for Future strike in the town of Davos that her demands to world leaders to stop investing in fossil fuels have been 'completely ignored'

The 17-year-old Swede addressed Davos for the second time this year, demanding that business and countries immediately stop investing in the fossil fuel industry and cancel all subsidies for the fuels

Thunberg joined dozens of climate activists in Davos for a protest on Friday, as part of the school-strike movement that has spread around the globe and led to pressure on governments to step up their response to climate change

Swedish climate activist Greta Thunberg marches during a 'Friday for future' youth demonstration in a street of Davos

'Is she the chief economist? Who is she? I'm confused,' he said, adding after a pause that it was 'a joke.'

Asked about Mnuchin's comments, the Swede said: 'Of course it has no effect. We are being criticised like that all the time.'

'If we cared about that, we would not be able to do what we do. We put ourselves in the spotlight.

'The situation is not being treated like the crisis it is.'

Greta's remarks earned her a rebuke from US treasury secretary Steve Mnuchin, who told her to 'study economics' and branded her 'a joke'

The spat between Mnuchin and Thunberg underlined the tensions over climate change at the World Economic Forum, where governments and major firms have come under pressure to act now on global warming.

In a speech on Tuesday, US President Donald Trump castigated the 'prophets of doom' that predict a climate 'apocalypse', in comments widely seen as an attack on Thunberg who sat in the audience.

But either by accident or design, there was no meeting between Trump and Thunberg at the forum.

Thunberg, who was selected as Time's Person of the Year for 2019, has returned to the World Economic Forum's annual summit in Davos, Switzerland, this week to press her call for businesses, world leaders and others to take action in the face of scientific evidence showing that temperatures on Earth are rising.

She spoke to reporters along with four other young climate activists, before they set off through the streets of Davos for the latest weekly 'Fridays for Future' campaign that she launched.

At the news conference, Thunberg sought to share the spotlight, deferring to her fellow activists: Vanessa Nakate of Uganda, Loukina Tille of Switzerland, Luisa Neubauer of Germany, and Isabelle Axelsson of Sweden.

3,000 world leaders in politics and business have gathered in Davos this week for the 50th annual World Economic Forum

Greta spoke at the forum for the second year running this year, telling leaders that 'our house is still on fire and your inaction is fuelling the flames by the hour'

This year's forum was called Stakeholders for a Cohesive and Sustainable World, in a hat-tip to climate activists