Swedish schoolgirl climate change activist Greta Thunberg told a packed room in the Palace of Westminster her future and those of her fellow children had been "sold".
She said: "We probably don't even have a future any more.
"That future has been sold so that a small number of people can make unimaginable amounts of money.
"It was stolen from us every time you said 'the sky is the limit'."
Experiencing microphone problems in Portcullis House, she asked: "Is this microphone on? Can anybody hear me? Is my English OK? I am starting to wonder."
She added: "The basic problem is the same everywhere and the basic problem is that nothing is being done...
"You don't listen to the science because you are only interested in the answers that will allow you to carry on as if nothing has happened."
When asked what she would say to US President Donald Trump, who has repeatedly cast doubt on the evidence to support climate change arguments, Greta said there was nothing she could say as he would not listen.
She said: "If I were to speak to Donald Trump today, I don't think there is much I could say to make him change his mind.
"Obviously, he must have scientists coming to talk to him all the time, so he is obviously not listening to the scientists.
"There is nothing I could say."
Greta had earlier met political leaders including Labour leader Jeremy Corbyn, Green MP Caroline Lucas and the Westminster leaders of the SNP and Plaid Cymru, Ian Blackford and Liz Saville Roberts.
But, Prime Minister Theresa May was "empty chaired" - a place left vacant at the roundtable meeting, complete with name sign but with no sign of Mrs May.
No.10 said she was busy chairing a Cabinet meeting, but environment secretary Michael Gove told her at the later event: "Suddenly, in the past few years, it has become inescapable that we have to act.
"The time to act is now, the challenge could not be clearer, Greta you have been heard."
Labour leader Jeremy Corbyn tweeted an image of himself and Miss Thunberg in front of a portrait of Tony Benn.
He wrote: "It was a pleasure welcoming UK youth climate strikers and @GretaThunberg to parliament.
"Young people will be the most affected by climate change - seeing them take charge of their future is inspiring.
"Labour's committed to working with young people campaigning to save our planet."