NUN OF THAT: The giant jeans ad has offended Naples natives as the city prepares for Pope Francis' visit.

A massive billboard showing a bare-breasted nun will greet Pope Francis during next weekend's official visit to Naples.

Erected by fashion label Rosso di Sera, the giant 6x9-metre sign hangs several storeys above the southern Italian city's centre.

Offended local residents and mortified Catholic officials have reacted with anger at the billboard, seemingly timed to coincide with the Papal visit.

Showing a model in a nun's habit and jeans, clutching rosary beads to her naked breasts, a Rosso di Sera statement denied the timing was deliberate.

It also said that there was "no intent to blaspheme" and that it was simply a "strong marketing choice".

It has been slammed as 'obscene' but the fashion label told Reuters that "trivialising the act of prayer was not the intention in any way."

One self-proclaimed atheist's comment on Facebook showed that anger wasn't just confined to the city's devout: "I find it offensive to intelligence, to women, to good taste and to faith."

Italian media has reported that the company has indicated that it may agree to remove the billboard if asked to by the national advertising watchdog.