The head of Germany’s Social Democrats (SPD), Martin Schulz, has resigned to ease preparations for a coalition government with Chancellor Angela Merkel’s conservatives.
Mr Schulz said he was handing over to a left-winger, Andrea Nahles, with immediate effect. However, SPD members have to vote on the change on 22 April.
SPD sources say Hamburg mayor Olaf Scholz will be interim leader.
Martin Schulz stepped down saying he wanted to end SPD “personnel debates”.
The SPD has agreed on a blueprint for coalition government with Ms Merkel’s Christian Democrats (CDU) and her Bavarian CSU allies.
SPD members will vote on the coalition deal next month – the result is expected on 4 March.
The centre-left SPD is on course to run six ministries, including finance and foreign affairs.
Mr Schulz, formerly European Parliament president, has said he will not serve as foreign minister. He has faced strong criticism inside the SPD.
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There has been more than four months of coalition negotiations – a German post-war record – since inconclusive elections in September.
A breakthrough was finally announced last week, with major concessions given to the SPD.
Many in the SPD fear that re-entering a coalition with the CDU/CSU could damage the party in the long term.
The SPD and CDU both had their worst results for decades in the election, which catapulted the far-right Alternative for Germany (AfD) into parliament for the first time, with 94 seats.