Although filmed at a £10 million re-creation of Rome in the city’s Cinecitta studios, the Italian state broadcaster RAI was so shocked at the scenes of violent copulation, stabbings and a crucifixion that it will screen an edited version next year.

Paola Masini, an RAI executive, said: “We realised from the start that the makers of Rome had a different concept of Ancient Rome than we do.

“If we had broadcast the version being shown in Britain or America, it would have been incomprehensible to Italians.”

For transmission in Italy next spring a “parallel” Italian version was made, with “excessively violent or sexual scenes” toned down or cut back.

The BBC is likely to fall foul of Ofcom, the industry regulator, by broadcasting the series when children are likely to be watching.

Rome, a £60 million co-production with HBO, features male and female full-frontal nudity, violent sex, crucifixion and throat-slashing within minutes of its 9pm start time.

Ofcom has warned broadcasters that the 9pm watershed must not become a “waterfall” after parents complained that material unsuitable for children was broadcast immediately afterwards. But the BBC said that it would not cut the series, which will run on Wednesdays on BBC Two. Rome’s creators said they were offering an authentic depiction of brutal life in the Republic and accused modern audiences of being more prudish than the Romans.

Bruno Heller, the series writer, said: “We are used to mediated depictions of sex and violence — you can find both on the internet at 8am if you want.

“The Romans took an unabashed and direct enjoyment in sex and violence. Our series might be shocking but it is based on source material.”

The BBC contributed £10 million to the 11-part series made in partnership with the creators of The Sopranos, and RAI. It follows the career of Julius Caesar from his conquest of Gaul to his assassination in 44BC.

Jonathan Stamp, an award-winning BBC ancient history documentary-maker with a First Class Oxford classics degree, acted as consultant on the series, which stars a British cast.

But the drama, which attracted four million viewers from its first episode in the US, is far more explicit than I Claudius, the BBC’s 1976 adaptation of the Robert Graves novel, and the corporation is steeled for complaints.

The scenes of sex and violence were justified to advance the story and BBC Two viewers expect to see challenging programming, the corporation argued.

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