Ernst Zundel, 66, author of books such as The Auschwitz Lie, was extradited from Canada, to which he had emigrated in the 1950s, and flown to Frankfurt in March after years on the run from the German authorities.
Mr Zundel appeared in court in Mannheim yesterday dressed in a dark suit and pale shirt to face charges of incitement to racial hatred and libel and accusations that he had used "pseudo-scientific methods" to deny the existence of the Holocaust,a criminal offence in Germany.
Mr Zundel, who appeared unmoved as the charges were read, was also accused of spreading biased views through books and his website, the Zundelseite, which is regularly visited by white supremacists and Nazi sympathisers worldwide.
The trial, which was attended by Mr Zundel's wife, Irma Rimland, and dozens of his supporters, began with a furious row. The presiding judge objected to the fact that Mr Zundel's defence team had recruited the German neo-Nazi lawyer Horst Mahler to act as their legal adviser. Amid loud protests and threats that he would be forcibly removed from the courtroom, Mr Mahler, who has been banned from working as a lawyer in Germany, was ordered off the defence team and told to watch the trial from the public gallery.
Mr Zundel's lawyers claimed the judge was attempting to prevent them from mounting an effective defence. Mrs Rimland described the charges against her husband as "politically tainted". If convicted, Mr Zundel could be jailed for five years.
The trial marks the end of a lengthy cat-and-mouse game involving Mr Zundel and the German and Canadian justice authorities. He had claimed immunity because of his Canadian residency, but German prosecutors finally obtained a warrant for his arrest in 2003 after judges ruled that as his website could be read in Germany, he could be brought to trial there. In March Canada judged him a security threat and ordered his deportation.