BERLIN -- Angela Merkel's main challenger in next year's German elections says the chancellor has an advantage over him because she is a woman.

Peer Steinbrueck's told weekly Frankfurter Allgemeine Sonntagszeitung in an interview published Sunday that Merkel had a "women's bonus" that counted in her favour.

He suggested female voters appreciated that the two-time chancellor is able to get her way within her party and in Europe.

The centre-left Social Democratic Party candidate's remarks sparked swift criticism from commentators across the political spectrum.

In the same interview, Steinbrueck said German chancellors aren't paid well enough. Merkel currently earns about (euro)18,000 ($23,729.40) a month.

Steinbrueck recently revealed that since leaving government in 2009 he has earned about (euro)1.25 million ($1.6 million) from speaking engagements on top of his salary as a lawmaker.