Faced with three years of almost zero growth, Merz has vowed to spend hundreds of billions using a special fund to rebuild creaky infrastructure, and give the economy a major boost in the process.

Merz's conservative CDU/CSU alliance and its SPD centre-left coalition partner reached agreement on a planned new law that would make it harder for green groups to hold up projects, particularly roads and canals.

"In future, clearer rules will apply to legal challenges against infrastructure projects," a document agreed between the parties said.

"Objections will only be considered if the person or association concerned has already participated in administrative proceedings at the planning stage -- this prevents abuse."

A bill setting out the new rules will be presented to parliament by the end of February at the latest.

Critics charge that suffocating bureaucracy both holds back business investment and makes revamping infrastructure move too slowly.

Stuttgart 21, a muti-billion-euro railway project in southern Germany notorious for its repeated delays, was held up for about 18 months after builders and conversationists locked horns over the discovery of two species of threatened lizard on work sites.

Holger Loesch, deputy head of the Federation of German Industries (BDI), said the proposal and other measures to speed up planning were "an important step" but urged the government to go further.

"Measures to speed up and simplify planning and approval procedures should also be extended to industrial plants in future," he said.

"The original coalition agreement also provides for comprehensive and binding deadline regulations, which are still missing from the proposed measures," he added.

But Juergen Resch, head of NGO Environmental Action Germany, told AFP that similar provisions limiting the right to object to projects were removed from German law after a 2015 ruling by the European Court of Justice.

"If you now want to reintroduce them, you are deliberately going against this ECJ decision," he said.