Data from Germany's Environment Agency show that even optimistic projections in the plan -- unveiled in March -- would not be enough to hit legally binding targets to cut climate-damaging emissions by 2040, according to Environmental Action Germany (DUH).

The group won a landmark case in January in a similar challenge to the prior government's climate action plan. The Federal Administrative Court ruled that Germany must outline realistic policies to achieve climate pledges.

Europe's biggest economy has set a legally binding 2030 target to cut greenhouse gas emissions by 65 percent compared to 1990 levels, and a 2045 deadline to achieve climate neutrality.

DUH said it would now ask the courts to enforce the January ruling against the government, and is also bringing a new lawsuit challenging specifics in the new plan.

"The German government has been failing to adequately meet its obligations for years," charged Barbara Metz, a national managing director at DUH.

Metz pointed to high emissions from building heating as particularly problematic.

Climate advocates have urged speed limits on Germany's famously fast motorways as another way to slash emissions.

Conservative Chancellor Friedrich Merz has promised to stick with Germany's climate pledges -- but also sought to scale back some climate-friendly regulations in an attempt to boost the country's stagnant economy and help heavy industry.

The policy framework unveiled in March included new electric car subsidies and a boost for the wind energy sector, among other items.

But Merz's government has looked to dial back solar expansion while pushing for a fleet of new gas-fired power plants, and fought to loosen EU-wide car emissions rules.