German Foreign Minister Frank-Walter Steinmeier, who hopes to defeat Chancellor Angela Merkel in a September election, has shortened his first name for the campaign to "Frank", a newspaper reported on Sunday.

To make the Social Democrat's name shorter, sound more modern and down to earth, his campaign has dropped the "-Walter" at rallies, on websites and in election literature.

"The name in my passport is 'Frank-Walter' and my friends call me 'Frank'," Steinmeier told the Bild am Sonntag, newspaper. "But I think there are more important problems facing our country right now."

Steinmeier's centre-left SPD, which relies heavily on support from unions and working class voters, trails Merkel's CDU by 10 percentage points before the September 27 election.