Austria warned it will go to court to try to halt the measure, while Germany -- which backed the inclusion of gas -- called extending the labelling to nuclear "unacceptable".

Critics of nuclear energy point to the threat posed by accidents and nuclear waste, while opponents of gas want to discourage investment in a fossil fuel technology they say only adds to the climate change crisis.

But the EU executive, under pressure from nuclear-powered France and gas-reliant Germany, argues that both have a role to play as cleaner power sources during the transition to a net-zero carbon future.

The decision "may be imperfect, but it is a real solution," EU commissioner Mairead McGuinness said.

While the EU is aiming for renewable energy to secure its low-carbon ambitions, she stressed that "we do not have the capacity for that yet -- but we still need to act urgently with all the means at our disposal".

The commission's announcement on Wednesday makes the labelling a done deal, unless a supermajority of EU countries, or a majority in the European Parliament, block it. Insiders said that was unlikely.

The controversy around the issue reflected the fact that EU countries each have very different energy mixes, and while they agree on climate change fighting goals they do not want to see disproportionate pain fall upon them to get there.

EU heavyweights Germany and France each rallied other member states around their respective backing of gas and nuclear.

But Germany -- which relies on Russia for most of its imported gas -- was scathing on nuclear being included in the labelling exercise, which Brussels calls its "taxonomy".

"Germany is clearly and unequivocally against the inclusion of nuclear power in the taxonomy," German Environment Minister Steffi Lemke said.

"Nuclear power is anything but sustainable," she said, calling its inclusion "a major mistake that will... endanger our climate targets".

Austrian Environment Minister Leonore Gewessler -- whose Alpine country produces most of its energy from hydropower -- was also critical, but of both nuclear and gas.

"The decision is wrong because it endangers the future... We are giving our children a backpack full of problems... It's irresponsible," she said.

Before the announcement, Austria, Denmark, the Netherlands and Sweden jointly signed a letter firmly opposing has projects as "largely incompatible" with the goals of the Paris climate agreement.

- 'Attempted robbery' -

In a sign of the hurdles faced by the commission in pushing through the labelling text, agreement among the EU's 27 member states was not unanimous. A vote had to be held before the announcement.

Green activists, too, expressed outrage.

Greenpeace sustainable finance campaigner Ariadna Rodrigo said: "I'd like to report an attempted robbery, please.

"Someone is trying to take billions of euro away from renewables and sink them into technologies that either do nothing to fight the climate crisis, like nuclear, or which actively make the problem worse, like fossil gas."

But McGuinness defended the decision, and argued that the plan imposes safeguards on how nuclear and gas projects are conducted under sustainable finance rules.

The fight over the European Union's classification of power sources is the latest dust-up in discussions between the member states on how to achieve a net zero-carbon economy by 2050.

Brussels had high hopes that the EU would help set a global standard on determining sustainable projects and direct big flows of Wall Street money towards saving the planet.

Berlin and Paris were adamant that their chosen energy industries are fit to receive the Green label and the commission -- the EU executive -- was handed the politically poisonous task of reconciling the positions.

To win the label, gas and nuclear projects are subject to constraints: projects must be approved by 2030 and 2045 respectively, as well as meet a long list of sector-specific criteria.