The European Union's top official has 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 that 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. However, 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," Ms von der Leyen said.

She promised a "new growth strategy" that "gives back more than it takes away", aiming to mobilise around €100 billion 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.

It comes as a United Nations global climate summit is under way in Madrid - focusing attention on the crisis - and on the eve of Ms von der Leyen's first EU summit.

Various leaked versions of the plan have been flying around Brussels for weeks, and lobby groups from all sides of the debate have been piling on pressure.

The European Parliament was the first to officially receive the plan.

"At this point, we can't yet say if it's a Green Deal or green washing," said French Green MEP Karima Delli as associations feared the proposals did not go far enough.

The leaders of EU member states will hear it tomorrow at their Brussels summit and Ms von der Leyen's deputy Frans Timmermans will take it to this week's COP25 forum in Madrid.

Young climate activists pictured at the COP25 forum in Madrid

"It's important that, in parallel to the announcement, there's a signal" of support from European leaders, European Council President Charles Michel said.

The "European Green Deal" lists legislative proposals, financial instruments and action plans in different sectors, with a timetable.

The key goals are to use a combination of cleaner tech and carbon capture methods to make Europe the first "carbon neutral" economy by 2050.

Three countries still highly dependent on fossil fuels, particularly coal, could still block the way: Poland, Hungary and the Czech Republic.

To convince them, the Commission plans to establish a €100bn "transition mechanism" to help them transition to renewable energy sources.

"It would help if at the Council we get some progress on carbon neutrality," said MEP Pascal Canfin, chair of the environment committee of the leaders' meeting.

The European Commission wants to set a target of cutting greenhouse gas emissions by 50 or even 55% by 2030, up from its 40% goal.

But for some this does not go far enough.

"The promises are too small, too few, and too far off," said Jagoda Munic of Friends of the Earth Europe.

"We're on a runaway train to ecological and climate collapse and the EU Commission is gently switching gears instead of slamming on the brakes."

The action plan also includes plans to extend the EU Emissions Trading System into the highly polluting shipping sector.

There are plans for a "border adjustment mechanism" aimed at importers to ensure that EU companies do not lose out to competitors who flout the Paris Climate Agreement.

The Commission will also lay out the timetable for its "from farm to fork" strategy to promote sustainable and quality agriculture, as well as that on biodiversity.

But however ambitious Ms von der Leyen's environmental plan is, it will be very dependent on the money EU members are willing to spend on it.

For the moment, this is the unknown. Negotiations for the multi-year budget for the period 2021-2027 are running late and entering a difficult stage.