The 19-year-old says she will not be attending the United Nations event, branding it an opportunity for "greenwashing, lying and cheating" by people in power.
The Swedish activist — who gained recognition at the age of 15 when she began spending her Fridays sitting outside the Swedish parliament building calling for more serious action on climate change — called out next month's summit for being "held in a tourist paradise in a country that violates many basic human rights".
Speaking on Sunday at London’s Southbank Centre to promote her new book, The Climate Book, she said: “I’m not going to COP27 for many reasons, but the space for civil society this year is extremely limited.
“The COPs are mainly used as an opportunity for leaders and people in power to get attention, using many different kinds of greenwashing.”
Greenwashing is the practice of falsely giving an impression that actions or products are more environmentally friendly than they are.
Ms Thunberg criticised leaders amid earlier reports that Prime Minister Rishi Sunak may not be attending the conference.
“Many world leaders are too busy to go there because they have their own problems,” she said.
“With that mindset we’re not going to be able to solve many of the problems that we face.”
Ms Thunberg also defended the actions of groups such as Just Stop Oil and Extinction Rebellion, which have blocked roads and vandalised artwork and buildings as part of protests which have been met with anger by some members of the public.
Asked if it matters if the groups upset people, Ms Thunberg said: “There are such a variety of different actions, so I can’t really generalise.
“We are right now in a very desperate position. Many people are becoming desperate and are trying to find new methods because we have realised that what we have been doing up until now has not done the trick.
“It’s only reasonable to expect these kinds of different actions and trying out different methods.
“Upsetting anyone depends on how you define upsetting anyone. Harming people is one thing and making people annoyed is a different thing.
“I think if groups in countries like the UK and Sweden get the media attention, I think it is very important to focus on the crisis that is happening.”
The Climate Book is a collection of more than 100 contributions from figures such as economist Kate Raworth, writer and activist Naomi Klein and author Margaret Atwood.