Germany's centre-left Social Democratic Party nominated Martin Schulz as its chairman and party candidate to take on Angela Merkel in the country's forthcoming federal elections.

Accepting the party's nomination on Sunday (19 March), Schulz vowed to fight populism if his party wins the elections in September.

A former president of the European Parliament, Schulz was nominated with 100% of the votes, the first time the party has unanimously nominated a candidate.

The party has been a junior partner in the country's coalition government since 2013. It hopes that Schulz will boost its chances of winning a majority.

Merkel's Christian Democratic Union party currently leads in polls, but Schulz's popularity compares favourably with Merkel, who has announced her intention to stand for a fourth term.

Accepting the nomination at the party's conference in Berlin, Schulz criticised US President Donald Trump and pledged to defend the European Union.

"Those who want to do away with this bloc will find in me an energetic opponent," Schulz said. "Anyone who thinks you can separate national interests from Europe is wasting away the future of Germany."

He denounced Trump's "misogynistic, anti-democratic and racist" rhetoric.

Schulz replaces Sigmar Gabriel as party chairman, who had trailed Merkel in head-to-head polls.