The Swedish environmental campaigner told EU leaders at the European Parliament in Brussels that they should “prove that you mean it” when it comes to tackling the threat to “life on Earth as we know it”.
Describing the bloc’s climate law as “empty words”, the 17-year-old said: "You said that this was an existential treat, now you must prove that you mean it.
"We will not be satisfied with anything less than a science-based pathway that gives us the best possible chance to safeguard the future living conditions for humanity and life on earth as we know it.
"Anything else is surrender: this climate law is surrender, because nature doesn't bargain, and you cannot make deals with physics. We will not allow you to surrender on our future.”
The EU has set a target of 2050 to reach net-zero carbon emissions - the same as the target set by the UK Government.
However, the terms of the Paris climate agreement state that richer countries are expected to reach the target quicker – something that Thunberg highlighted.
She went on: "We don't just need goals for 2030 or 2050, we above all need them for 2020 and every year to come.
“We need to start cutting carbon emissions drastically at the source, now. Your distant targets will mean nothing is high emissions continue for business as usual even for just a few more years, because that will use up our remaining carbon budget before you have the chance to even deliver on your 2030 goals.”
She added: "When your house is on fire you don't wait a few more years to start putting it out. And yet, this is what the Commission are proposing today.
"When the EU presents this climate law and net zero by 2050 you indirectly admit surrender: that you are giving up on the Paris agreement, giving up on your promises and giving up on doing everything that you possibly can to ensure a safe future for your children."
Defending the new law, President of the Commission, Ursula von der Leyen, said: “We are acting today to make the EU the world’s first climate neutral economic bloc by 2050.
“The Climate Law is the legal translation of our political commitment, and sets us irreversibly on the path to a more sustainable future. It is the heart of the European Green Deal.”
Executive Vice-President for the European Green Deal, Frans Timmermans, added: “We are turning words into action today, to show our European citizens that we are serious about reaching net-zero greenhouse gas emissions by 2050. The Climate Law will ensure we stay focused and disciplined, remain on the right track and are accountable for delivery.”