German Chancellor Angela Merkel's challenger for power in next year's elections stoked controversy on Sunday after saying his rival enjoyed a popularity bonus with women and that the job paid too little.

In an interview with the Frankfurter Allgemeine Sonntagszeitung weekly, the Social Democratic Party's (SPD) candidate for chancellor, Peer Steinbrueck, said: "Angela Merkel is popular because she gets a bonus from women."

"A large proportion of female voters appreciates how she has for a long time asserted herself in her party but also, beyond that, in Europe. That is not a disadvantage for me, but an advantage for her," he said.

Polls show that Merkel's conservatives enjoy a significant lead over the opposition SPD and the German leader herself remains one of the country's most popular politicians ahead of elections on September 22.

Steinbrueck, whose campaign got off on the wrong foot after it emerged he received some 1.25 million euros ($1.65 million) in fees for making speeches at private functions, also said German chancellors should earn more.

"A German chancellor earns too little, when the demands on him or her are taken into account and when compared to other jobs with fewer responsibilities and much bigger salaries," Steinbrueck was quoted as saying.

"Almost every bank manager in North Rhine-Westphalia earns more than the chancellor," he added, referring to a wealthy region in western Germany.

A German chancellor earns approximately 17,000 euros per month.

The influential Spiegel newsweekly commented on its website that the challenger was "lurching from disaster to disaster."

"Maybe he didn't mean it that way, but the words of the SPD candidate about his ... opponent were chosen very clumsily," Spiegel commented.

Meanwhile mass circulation Bild, Europe's most widely read newspaper, also criticised the challenger.

"Peer Steinbrueck wants to put social justice and community at the heart of his election campaign. But he keeps making everyone talk about his income and his wealth," the paper commented.