No editor of Germany's right-wing, mass-circulation Bild newspaper could ever expect to be liked by the country's left-wing press. But what was mere mutual animosity has now erupted into an embarrassing and vitriolic row over the size – believe it or not – of the Bild editor's penis.

The dispute concerns a massively exaggerated phallus attached to an image of Bild editor and bane of the left, Kai Diekmann. His altogether striking endowment features prominently in a huge satirical mural on the outside wall of the office of Berlin's alternative left-wing Die Tageszeitung (Taz) newspaper.

The mural, by the artist Peter Lenk, was put up months ago. It was the latest weapon in the Taz campaign to mock Bild, whose offices are just opposite, as well as Diekmann, its flamboyant, hair-gelled, red-baiting 45-year-old editor.

Bild has a daily circulation of more than three million and offers its readers a mixture of sex, sport, crime and middle-of-the-road politics. Taz sells 65,000 a day and sees itself, in the tradition of 1968, as a bastion of the alternative left. It enjoys a reputation for poking fun at the German establishment. But the penis row now appears to have put that reputation at stake.

Four months ago, Taz appointed Ines Pohl, 42, a former anti-nuclear and women's rights activist, as its editor. Her brief was to return the paper to its left-wing roots after a much-criticised foray into more popular journalism.

Pohl is not amused by the mural. "If I comply with Peter Lenk's wishes, then I will have to lock up my bike underneath this six-metre-long willy every morning for the next two years," she said. "What a miserable piece of provocation, how pathetic. I am simply fed up with this kind of inflated petit bourgeois male power-game nonsense. Take it down." Unfortunately for Pohl, not all the journalists at Taz agree with her.

Meanwhile, the mural's intended object of ridicule, Kai Dieckmann, is enjoying a field day. Although he yesterday insisted to Der Spiegel magazine, "It can't be me, Peter Lenk has expressly denied that it is," he has certainly made the most of the association and has started a popular blog. He has also suggested a "peace party" for Bild and Taz journalists, with Bild paying for the drinks. Taz has yet to respond to his invitation.