A dozen environmental groups are starting legal challenges against the European Union’s executive branch in a bid to stop the inclusion of natural gas and nuclear power generation in the bloc’s list of sustainable activities.

European Union lawmakers in July voted to add natural gas and nuclear to the list, backing a proposal from the European Commission that has been drawing fierce criticism and accusations of greenwashing.

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ClientEarth, WWF’s European Policy Office, Transport & Environment (T&E), and BUND said on Monday that they have asked for an internal review of the decision to include gas. The European Commission has up to 22 weeks to reply and the groups say they will take the action to the Court of Justice of the EU if the executive arm refuses to reconsider its move.

They said that “gas is a potent fossil fuel that threatens European energy security and has led to sky-high energy prices across Europe.”

The groups argue that giving gas a sustainable label clashes with other EU laws and does not respect the EU’s commitments and obligations under the 2015 Paris accord’s target for limiting global warming.

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Separately, eight Greenpeace organizations in Europe have taken action over the inclusion in the so-called taxonomy delegated act of both fossil gas and nuclear energy. They, too, have sent a request for internal review to the Commission, arguing that their inclusion is a breach of the taxonomy regulation.

The green labeling system from the European Commission defines what qualifies as an investment in sustainable energy. The EU’s executive arm did not initially include gas and nuclear and created divisions among member countries when it proposed their addition earlier this year.

The question of nuclear power has divided environmentalists, energy experts and governments for years, with some arguing it’s an important source of energy because it’s produced with no emissions and thus “clean,” while others say the risks of nuclear reactions are too great and infrastructure is slow and costly to build. Liquid natural gas, clearly a fossil fuel, is roundly criticized in environmental circles.

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Under certain conditions, gas and nuclear energy will now be part of the mix, making it easier for private investors to inject money into both.

With the EU aiming to reach climate neutrality by 2050 and to cut greenhouse gas emissions by at least 55% by 2030, the commission says the classification system is crucial to direct investments into sustainable energy. It estimates that about 350 billion euros of investment per year will be needed to meet the 2030 targets.

“This fake green label is incompatible with EU environment and climate laws. Gas is a leading cause of climate and economic chaos, while there is still no solution to the problem of nuclear radioactive waste and the risk of nuclear accidents is far too significant to ignore,” said Greenpeace EU sustainable finance campaigner Ariadna Rodrigo.