The EU's top official Wednesday launched the bloc's new "Green Deal", hailing it as a strategy for jobs and economic growth, not just for cutting emissions.

Unveiling the plan to the European Parliament, European Commission president Ursula von der Leyen also warned against the steep cost of inaction.

Earlier, she had compared the ambition of the plan to the 1960s US mission to the moon, but Green groups were quick to warn it does not go far enough.

The key element of the plan will be a law committing member states to build a carbon neutral economy by 2050 - but first it will need the go-ahead from parliament and EU leaders. "We do not have all the answers yet. Today is the start of a journey. But this is Europe's man on the moon moment," Ursula von der Leyen said. She promised a "new growth strategy" that "gives back more than it takes away", aiming to mobilise around 100 billion euros to fund clean energy projects.

"We have to make sure no one is left behind," she told reporters. "This transition will either be working for all and be just, or it will not work at all."

In parliament, she said: "Some say the cost of this transition is too high, let us never forget what the cost of non-action would be. It is rising by the year."

The document is the first major political challenge for the former German defence minister since she took charge of the European Commission this month. And it comes as a UN global climate summit is under way in Madrid - focusing attention on the crisis - and on the eve of von der Leyen's first EU summit.