Sigmar Gabriel, the German foreign minister, said voting for the far-right AfD party could put "Nazis back in the Reichstag" on Monday, in an insult rarely heard in national politics.

In an interview with the local media, Mr Gabriel said many German voters were considering voting Alternative fur Deutschland in the upcoming election as they felt their concerns about migration, security and jobs were not being addressed.

"If we're unlucky, then these people will send a signal of dissatisfaction that will have terrible consequences. Then we will have real Nazis in the German Reichstag for the first time since the end of World War Two," the Social Democrat told t-online.de.

His comments were unusually strong given Germans' continued sensitivity to Nazi references, even 70 years after the war ended.