MEPs in the eastern French city of Strasbourg were to take their position on the measure in a vote set for 1000 GMT with opponents and backers furiously lobbying their side.

"If we really want to meet these climate objectives, we must also be able to finance them," Czech Prime Minister Petr Fiala told a session of parliament to mark his country's taking over of the EU presidency.

The green label, known in EU parlance as the "taxonomy", "caters to a number of countries that will only be able to meet their climate targets as a result of these criteria", he warned.

A small but influential group of member states is meanwhile asking MEPs to reject the green label, in a coalition of opponents to nuclear and gas.

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

"How can we ask other countries to reduce their use of fossil fuels if we classify them as green? This will undermine the Paris agreement," said Dutch Green MEP Bas Eickhout.

Critics of nuclear energy 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.