BRUSSELS — The European Union laid out plans on Wednesday for a climate law that would set a target of net zero carbon emissions across the bloc by 2050.

But the bill, part of a wider policy package called the Green Deal, was immediately criticized by climate activists, including Greta Thunberg, who denounced it as “empty words.” Many activists had called on the bloc to set a 2030 target, and to specify now how it would be achieved.

European officials had hoped to win the support of Ms. Thunberg, the 17-year-old Swedish activist, when they met with her in Brussels on Wednesday. But she went on instead to tell the European Parliament that the proposal amounted to “giving up on the Paris Agreement,” the pact signed in 2016 under which almost 200 nations promised to limit their emissions, and from which the United States has withdrawn.

Ursula von der Leyen, the president of the European Commission — the bloc’s executive arm, which formulated the bill — described it as “a compass for the next 30 years.” If passed by the European Parliament and its 27 member states over the next several months, it would require the commission to factor climate goals into every piece of legislation.