The European Parliament in July approved a European Union proposal giving a sustainable finance label to investments in gas and nuclear power, sparking claims of "greenwashing" by environmental lobbyists.

The daily Kurier reported that Vienna filed the challenge with the European Court of Justice (ECJ), ahead of a deadline on Monday, but gave no source.

Austria's climate ministry stopped short of confirming the report.

"Our position has not changed. We have said from the beginning that we will file a complaint," a ministry spokeswoman told AFP.

ECJ officials in Luxembourg, the tribunal's headquarters, did not immediately return a request for comment.

The European Commission had defied protests from green campaigners and dissent in its own ranks to put a green label on gas and nuclear power.

It had argued that both have a role to play as cleaner power sources during the transition to a net-zero carbon future.

Environment Minister Leonore Gewessler has vowed Austria would file legal action against labelling nuclear energy as green, describing it as "outdated" and "too expensive" and highlighted safety concerns and uncertainty over how to deal with nuclear waste.

The Alpine nation of nine million people -- which depends heavily on gas -- has been fiercely anti-nuclear for decades.

An unprecedented vote by its population in 1978 prevented its only nuclear plant -- meant to be the first of several -- from starting operations.

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