Can natural gas ever be called sustainable? And can nuclear energy credibly be dubbed green?

A landmark proposal from the European Commission effectively answers “yes” to both — and many are not pleased.The European Union’s executive arm on Wednesday presented a plan to classify some natural gas and nuclear power as green investments, a move that may shape the climate fight in Europe and around the world.

What’s known as the “E.U. taxonomy” sets out to define a sustainable investment to guide spending toward projects that are in line with the bloc’s climate goals. A draft text, circulated on New Year’s Eve, included gas and nuclear. On Wednesday, officials confirmed they will be included as “transitional activities.”

The inclusion of gas was backed by several member states that said gas is needed as a “bridge,” as countries wean themselves off fossil fuels and build up their renewables capacity. France and others pushed for the inclusion of nuclear energy — despite strong opposition from Germany.

The backlash has united some E.U. countries and advisers, environmental groups and even asset managers in criticism. They charge that the commission has turned its own bid to “protect private investors from greenwashing” into greenwashing on a grand scale, undermining E.U. goals and credibility.

“Nuclear power is neither ‘green’ nor sustainable,” Austrian Chancellor Karl Nehammer wrote Wednesday on Twitter. “I cannot understand the decision of the EU.”

Austrian climate minister Leonore Gewessler previously called the inclusion of gas and nuclear in the draft a “cloak-and-dagger operation.” Her country, along with Luxembourg, another fierce opponent of nuclear energy, has threatened to sue the commission over the rules.

Greenpeace denounced the proposal as an “anti-science plan” that “represents the biggest greenwashing exercise of all time.” The CEO of a group representing investors including BlackRock and Vanguard — hardly hippies — wrote in an open letter to E.U. representatives that including gas would “seriously compromise Europe’s status as a global leader in sustainable finance.”

The commission defended the plan, calling it, among other things, “a means to an end” and noting that investment rules for natural gas and nuclear energy will come with stipulations.

Faced with questions from the media about whether the move undermines Europe’s credibility on climate, Mairead McGuinness, the European commissioner responsible for financial services, said Wednesday that the commission’s “credibility is actually enhanced by doing something difficult but necessary.”