The world is speeding in the wrong direction in tackling the climate emergency, Greta Thunberg has said, before a UN event at which national leaders have been asked to increase their pledges for emissions cuts.

Thunberg, whose solo school strike in 2018 has snowballed into a global youth movement, said there was a state of complete denial when it came to the immediate action needed, with leaders giving only distant promises and empty words.

The fifth anniversary of the Paris climate accord is on Saturday and should have seen countries set out new plans to keep global heating below 2C and close to 1.5C. Current pledges would mean a catastrophic 3C rise in temperatures.

But the planned summit has been postponed because of the coronavirus pandemic until next November and a virtual one-day UN meeting will take place instead, involving up to 70 world leaders. The European Union will also try to agree a new 2030 emissions target on Friday at a Brussels summit.

Thunberg has released a video which calls leaders to account for failing to reverse rising carbon emissions. “We are still speeding in the wrong direction,” she said. “The five years following the Paris agreement have been the five hottest years ever recorded and, during that time, the world has emitted more than 200bn tonnes of CO2.

“Distant hypothetical targets are being set, and big speeches are being given,” she said. “Yet, when it comes to the immediate action we need, we are still in a state of complete denial, as we waste our time, creating new loopholes with empty words and creative accounting.”

She told the Guardian: “Leaders should be telling the truth: that we are facing an emergency and we are not doing nearly enough. We need to prioritise the action that needs to be taken right here and right now, because it is right now that the carbon budget is being used up.

“We need to stop focusing on goals and targets for 2030 or 2050,” she said. “We need to implement annual binding carbon budgets today.”

Thunberg said recent pledges by the UK – to cut carbon emissions by 68% by 2030 compared with 1990 levels – and by China, Japan and South Korea to become net carbon zero were creating a sense of progress, and she added: “That is a very dangerous narrative because of course we’re not going in the right direction. We need to call this out.”

But Thunberg, who has given speeches at previous UN climate summits, concludes her video message by saying: “There is hope … we are the hope – we, the people.”

She said: “For me, the hope lies in democracy – it is the people who have the power. If enough people stand up together and repeat the same message, then there are no limits to what we can achieve.”

The Fridays for Future movement of youth climate strikers expects more than 2,500 protests to take place on Friday, though like Thunberg’s, many will be online due to Covid-19 restrictions.

Adélaïde Charlier, from Fridays for Future Belgium, said: “All decisions not taken now will fall back on our generation’s shoulders. [Coronavirus] has had a huge impact, we cannot deny that. But what’s incredible is seeing the energy inside a movement that does not want to die, but wants to continue to push through.”

Vanessa Nakate, from Fridays for Future Uganda, also had a stark message for leaders: “You have already determined our present, which is obviously catastrophic. Now fix the future, and start now. You have everything you need to stop this war against the planet and the people. But you just won’t do it. We want deep cuts from you right now.”

“I see the hope in the young people who are speaking out from different parts of the world,” Nakate said. “But the only way we can strengthen that hope is to continuously create awareness about the challenge that we are facing, so that we get everyone involved.”

Parents’ climate action groups are also targeting leaders in the run-up to the UN and EU summits. At the latter, Poland and Hungary are threatening to block a deal.

Marzena Wichniarz, from Parents for Future Poland, said: “I was pregnant with my daughter when the Paris agreement was signed. It was an amazing message to the world: leaders pledged to fight for a better future for all our children. But we are disappointed, in fact furious, with the Polish government now.”

Agnes Imgart, from Parents For Future Global, said: “Our children have changed so much in the last five years, but the Paris agreement is still crawling.”