Teenage climate activist Greta Thunberg on Friday said calls to the corporate elite meeting in Davos to immediately disinvest in fossil fuels had been ignored.

"We had a few demands (coming into the World Economic Forum). Of course these demands have been completely ignored. We expected nothing less," Thunberg told reporters in the Swiss ski resort on the last day of the conference.

Thunberg was a highlight of the 50th edition of the conference, drawing massive attention including barbs by US Secretary Steven Mnuchin who on Thursday told the teen to go "study economics".

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."

Swedish climate activist Greta Thunberg marched in a "Friday for future" youth demonstration in Davos on Friday on the sideline of the World Economic Forum (WEF) annual meeting Swedish climate activist Greta Thunberg marched in a "Friday for future" youth demonstration in Davos on Friday on the sideline of the World Economic Forum (WEF) annual meeting Photo: AFP / Fabrice COFFRINI

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

Asked about the 17-year-old's demand for an immediate halt to investment in fossil fuels, Mnuchin said on Thursday:

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

"After she goes and studies economics in college, she can come back and explain that to us."

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.