A lawmaker for Germany's Social Democrats (SPD) has called for unity as lawmakers were set to vote in a second secret ballot to elect conservative Friedrich Merz as the country's new chancellor, after a historic defeat in a first round earlier on Tuesday.

German conservative leader Friedrich Merz failed to secure enough parliamentary votes to become chancellor in a major blow.

Friedrich Merz has succeeded in his bid to become the next German chancellor during a second vote in parliament, hours after he suffered a historic defeat in the first round.