The reporter who exposed the motor racing chief Max Mosley's S&M orgy insisted yesterday to a judge that the day-long sex party in a basement flat had an overwhelmingly Nazi theme.

Neville Thurlbeck, chief reporter of the News of the World, stoutly defended his claim that the son of the British fascist leader Sir Oswald Mosley had re-created a concentration camp scenario for his group spanking session. Mr Thurlbeck said he was entitled in the public interest to plant a hidden camera in the apartment in Chelsea, West London, to gain proof that Mr Mosley was engaged in canings so violent that they could be classified as criminal assaults.

During a lengthy and robust cross-examination at the High Court, the reporter tore into a suggestion by Mr Mosley's counsel James Price, QC, that the S&M orgy was “clearly” on the theme of guards and prisoners in an English jail.

Mr Thurlbeck said: “I don't know an English prison where inmates are beaten on their bottoms with a stick until their bottoms bleed. I know of no English prison where the warder will deliver those blows and count them out in German. I know of no English jail where the inmates then have sexual intercourse with the warder who has just administered the blows.”

He scorned the idea that his informant, a dominatrix who was paid to smuggle a secret camera into the orgy, had merely been joining in a German-themed fantasy rather than an unmistakably Nazi one.

“She took part in lice inspection,” Mr Thurlbeck said. “She took part in hair shaving. They took part in the use of fake German accents. They took part in beatings that were counted out in German surrounded by girls in German military uniform. It certainly wasn't Hansel and Gretel.”

The reporter was challenged over e-mails he sent to the party organiser, a full-time professional dominatrix, and a German woman she recruited, asking them for exclusive interviews as a follow-up to his original exposé.

He wrote that if they agreed to tell all he would give them £8,000, pixillate their pictures and preserve their anonymity. Otherwise he would have to write the best story he had, based on a trawl through their websites.

“You are giving them a choice between co-operating, giving you an interview and getting paid,” Mr Price said. “If they don't, they get their pictures in the newspaper in the most embarrassing and humiliating circumstances.” Mr Thurlbeck replied: “I am offering money for an anonymous interview. I am not blackmailing at all.” His Editor, Colin Myler, asked about the same e-mails during his evidence, accepted that they could be seen as threatening but disagreed that this was a case of blackmail.