Germany is rethinking its plan to exit nuclear power by the end of the year, as concern increases that Russia’s moves to cut gas supplies could trigger a winter electricity crunch in Europe’s largest economy.

A U-turn on nuclear power would mark a big departure in German energy policy. It would be a particularly bitter pill for the Greens, a pillar of chancellor Olaf Scholz’s coalition government with roots in the country’s anti-nuclear movement.

A person close to the Greens leadership said the party had come to the conclusion that “all options should be on the table” in the event of an energy crunch. One of those options might be to extend the life of the Isar 2 nuclear station in Bavaria beyond its shutdown date of December 31.

The person said the extension would only be for a few months, and any decision would be contingent on the results of a stress test that is under way to determine whether Germany’s electricity supply can continue to function even “under aggravated conditions”.

The stress test is expected to show that Bavaria, in particular, could face problems with its winter electricity supply. The state, a key industrial centre, has relatively little wind and solar energy and relies heavily on gas and nuclear for electricity.

A spokesperson for Scholz said the chancellor would also wait for those findings before deciding on a course of action. The government would take the decision in a “completely ideology-free and open-minded way”, the spokesperson added.

The nuclear rethink underscores how Russia’s escalating economic war with the west has led to a new willingness among Germany’s political class to abandon a signature policy brought in to hasten the green transition.

The latest sign of the Kremlin’s willingness to weaponise its energy exports came on Monday when gas giant Gazprom warned that flows through the Nord Stream 1 pipeline would be cut to 33mn cubic meters from Wednesday — just a fifth of its capacity and half of current levels. European gas prices soared on the announcement, hitting five-month highs.

The energy crunch has forced Scholz’s government to take decisions that go against typical Green policy, including restarting some of Germany’s highly polluting coal-fired power stations. His coalition had said it wanted to phase out coal plants completely, “ideally” by the end of the decade.

Germany decided to abandon nuclear power in 2011, in the wake of the Fukushima disaster in Japan. The three nuclear facilities still in operation — Isar 2, Emsland and Neckarwestheim 2 — are all due to close by the end of the year.

The government, made up of Scholz’s Social Democrats (SPD), the Greens and liberal Free Democrats (FDP), has stuck to its planned timetable for the nuclear phaseout even after Russia invaded Ukraine.

Green economy minister Robert Habeck has insisted Russian gas was largely used to heat homes and in industry — with nuclear playing no role in either. Greens have also stressed that the three nuclear plants accounted for just 6 per cent of electricity produced in Germany in the first quarter, much less than gas at 13 per cent.

But with many consumers switching from gas to alternative forms of energy, experts say electricity demand will grow — and nuclear could help plug the demand gap.

Pressure for a rethink on nuclear has been growing within and outside the government, with the FDP and opposition Christian Democrats demanding a reprieve for the three nuclear plants.

Even prominent Greens have shown flexibility on the issue. Katrin Göring-Eckardt, the Green deputy speaker of parliament, on Sunday said Bavaria had a “special problem” that could be addressed by allowing Isar-2 to continue operating beyond the end of the year.

Franziska Brantner, another influential Green who is a state secretary in the economy ministry, also implied in a TV interview that Germany might need to keep its nuclear plants running out of “solidarity” with France, which has been forced to shut many of its reactors because of corrosion problems and to import power from its neighbours.

Additional reporting by Valentina Pop in Brussels