Under current rules introduced in 2000, people born to a non-European Union family are allowed dual citizenships only as children. They must chose between nationalities before their 23rd birthday - or automatically lose their German passport.
“We've been demanding for a long time that this forced choice be abolished and we'll be bringing an initiative in the Bundesrat [upper house of parliament] to that effect,” Renate Künast, head of the Green party parliamentary fraction told Die Welt newspaper on Monday.
Künast said the obligatory choice at the age of 23 was unreasonable and a tough test of loyalty for young people from non-European immigrant backgrounds. The rule does not apply to children who have a parent from an EU country - they can retain dual citizenship.
“Dual citizenship is an expression of the diversity and openness of our society,” said Künast, suggesting Merkel's Christian Democratic Union (CDU) was behind the times with its opposition to non-EU dual citizenship.
“To deny that only shows how backward-looking the thinking of the CDU is," she said.
The initiative appears to be a clever bit of political manoeuvring by the opposition, which is keen to exploit its newly-won upper house majority and give Chancellor Angela Merkel as many headaches as possible in the five months to go before the general election.
Künast's comments on dual citizenship came on the second day of Merkel's state visit to Turkey, where Turkish Prime Minister Recep Tayyip Erdogan demanded the Chancellor abandon her opposition to dual citizenship.
The Greens' move also comes less than a week after the governing junior coalition partner the Free Democrats (FDP) catapulted the topic back into the headlines when Justice Minister Sabine Leutheusser-Schnarrenberger called for a change in the law.
By inserting the issue straight into the Bundesrat, the Green party and their allies the Social Democrats (SPD) could force the FDP to break ranks with their CDU coalition partner and support the initiative.
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The path through the upper house is another way of getting the lower house Bundestag to address an issue. If the SPD, Greens and the Left party use their opposition majority to pass an initiative in the Bundesrat, it will automatically pass to the lower house for discussion.