MEPs in the eastern French city of Strasbourg declined to reject the measure, which was backed by France and Germany.

There were 278 votes to stop it while 328 voted for a green light. There were 33 abstentions.

Czech Prime Minister Petr Fiala, whose country has just taken over the rotating EU presidency from France, tweeted that the result was "excellent news" for Europe.

"It paves the way towards energy self-sufficiency which is absolutely crucial for our future," he said.

The green label, known in EU parlance as the "taxonomy", for gas and nuclear is the only way that certain EU countries will "be able to meet their climate targets," he had warned before the vote.

A small but influential group of member states and activists had lobbied hard for MEPs to reject the label, in a coalition of opponents to nuclear and gas energy.

Critics of gas point to the war in Ukraine as the most urgent reason to reject the green label, saying that encouraging investment would only increase dependence on Russian supply.

"It's dirty politics and it's an outrageous outcome to label gas and nuclear as green and keep more money flowing to Putin's war chest," Greenpeace EU sustainable finance campaigner Ariadna Rodrigo said.

"We will fight this in the courts," she added.

Eco-campaigner Greta Thunberg tweeted that "the hypocrisy is striking" and argued that the parliament's adoption "will delay a desperately needed real sustainable transition and deepen our dependency on Russian fuels".

Critics of nuclear energy, meanwhile, point to the threat posed by accidents and nuclear waste and believe solar and wind energy is the best way forward.

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 EU hopes that its label will steer huge sums of private capital into activities that support climate goals.

Backers of the taxonomy insist that investment in gas and nuclear is a necessary step on "the route to sustainable energy sources," said German MEP Christian Ehler.

For this reason, the vote is a "wise decision" that will lead to more renewables down the road, he added.