Coal currently accounts for 40 percent of Germany's energy production

Germany's opposition Green party unveiled Monday a 10-point plan to end electricity generation from coal within 20 years, a key plank of its campaign heading into next year's general elections.

"We aim to introduce the end of the era in Germany, irreversibly and reliably in the coming parliamentary term," running to 2021, Green lawmakers wrote in the proposal, a copy of which was obtained by AFP.

As the smallest party represented in parliament, the Greens have been mooted as a potential kingmaker to Chancellor Angela Merkel's conservatives after the general election expected in September or October 2017.

Coal currently accounts for 40 percent of the energy mix in Europe's top economy and has been the focus of determined protests by environmental activists in recent years.

Keeping coal on life-support was an unexpected effect of Germany's exit from nuclear, a core demand of the Greens finally accepted by Merkel in a surprise u-turn after the 2011 Fukushima disaster in Japan.

However, Merkel's right-left government has been reluctant to move against coal at home for fear of putting tens of thousands of miners in the country's remaining brown coal pits out of work.

Now the Green party's MPs have suggested that an oversight commission be created to supervise a process which would see new open-cast mines forbidden, the most polluting coal plants closed immediately, and a "carbon dioxide budget" set for each remaining coal power plant—with the furnaces extinguished once the budget was used up.

Limits on airborne pollutants should be reduced, according to the plan, while coal plant operators should pay to offset environmental damage.

The Greens insisted that their plan would not push up costs, and that efficiency measures could drive the price of renewable energy down in future.

"Inflexible plants don't fit into the new world of electricity," they wrote. "In Germany, the move away from using coal began many years ago."

As for the miners, the Greens say, their numbers are already contracting sharply—meaning new jobs will have to be found for them whatever is done about .