An 18-year-old climate activist has called for Greenpeace to drop its “old-fashioned and unscientific” campaign against nuclear power in the EU.

In April, the environmental campaign group announced it would appeal against the EU Commission’s decision to include nuclear power in its classification system for sustainable finance. This “taxonomy” is designed as a guide for private investors wanting to fund green projects, aiming to boost environmental investment.

Ia Aanstoot, from Sweden, who for three years took part in the Friday school strikes movement started by Greta Thunberg, said Greenpeace’s legal challenge served fossil fuel interests instead of climate action.

With campaigners from five other EU countries, Aanstoot has launched the Dear Greenpeace campaign, asking the NGO to “drop your old-fashioned and unscientific opposition to nuclear power, and join us in the fight against fossil fuels instead”.

This week, Aanstoot submitted papers to the EU court of justice asking to become an “interested party” in the upcoming legal battle between the European Commission and Greenpeace. If the court approves the request, she and other pro-nuclear campaigners will be able to provide testimony in favour of nuclear power.

Greenpeace has argued that the EU classification system is “greenwashing” that allows nuclear power plants to receive money that otherwise would have gone to renewables. Lawyers acting for the NGO have said nuclear energy causes “significant harm to the environment” so should not be included in the taxonomy.

Aanstoot said: “Over a third of the clean energy in the EU is nuclear power, so Greenpeace’s motion to get rid of it is really harmful, I think. And I would definitely prefer to be working together with Greenpeace to get rid of fossil fuels. But when they are actively fighting such a large and useful tool like nuclear power, I don’t feel like I can work with them.

“Greenpeace is stuck in the past fighting clean, carbon-free nuclear energy while the world is literally burning. We need to be using all the tools available to address climate change and nuclear is one of them. I’m tired of having to fight my fellow environmentalists about this when we should be fighting fossil fuels together.”

She has joined with other young campaigners from Poland, Sweden, France, Finland and the Netherlands.

One of these, Julia Galosh, a 22-year-old biologist, said: “I’ve protested opposite Greenpeace in horror as they campaigned to stop Germany’s nuclear reactors – something which led to much more demand for coal. Now they want to stop my home country of Poland from transitioning from coal to nuclear. Enough is enough.”

Aanstoot thinks this is a generational issue, with younger environmentalists more keen on nuclear than those from older generations.

She said: “I feel like a lot of the arguments that are used from Greenpeace and other older environmentalist … are very identity-based. It nearly feels like being anti-nuclear is a question of identity for these older environmentalists. These old issues are ones that nuclear has mostly moved past, and also the global situation has changed. In the 60s and 70s during the anti-nuclear protests, the climate crisis was not as much of a concern as it is today.

“I feel like it’s just a matter of moving on with the times and the scientists have moved on – the IPCC Intergovernmental Panel on Climate Change now says that nuclear is a really important tool.”

A Greenpeace EU spokesperson said: “We have the greatest respect for folks who are worried about the climate crisis and want to throw everything we have at the problem, but building new nuclear plants just isn’t a viable solution. The top priority is to cut carbon emissions as fast and, ideally, as cheaply as possible, and nuclear fails on both scores. The new plant at Hinkley C is over a decade behind schedule and billions over budget. The next one in line, at Sizewell C, may not even start generating energy until today’s newborns turn teenagers. And the industry has no long-term solution for safely storing the radioactive waste that will remain dangerous for thousands of years.

“The good news is that we don’t need new nuclear. Solar and wind technologies are a much cheaper and quicker way to cut emissions, and with modern storage tech, 100 percent renewable systems are perfectly possible. Encouraging investments into nuclear energy by including it in the EU taxonomy risks diverting funding away from renewables, home insulation and support for people hit by extreme weather. We don’t have the luxury of endless time and resources so we should focus them on the solutions with the best chance of delivering.”