Richard Wagner fans rejoiced last week at the start of the 91st Bayreuth Festival: for the first time in memory this year's festival was about the music of Wagner and not the squabbling of his descendants.

In this age of Big Brother and The Osbournes, it's no surprise the real-life intrigues of the Wagner family overshadow the music. However, this year the family called a ceasefire in its battle over who would succeed Wolfgang Wagner, the 81-year-old grandson of the composer, as artistic director. Everyone was looking forward to the festival under the new young conductor, Christian Thielemann, and a premiere.

However, Thielemann comes to Bayreuth with a tarnished reputation. The 43-year-old conductor made an acclaimed debut as a guest conductor of Die Meistersinger at Bayreuth two years ago, receiving a 20-minute standing ovation.

But three months later his triumph was overshadowed by an accusation that he made anti-Semitic remarks about Daniel Barenboim, the Argentine-born Israeli pianist and conductor.

During a row between Barenboim and a conservative politician, it was alleged Thielemann said if Barenboim, the musical director of the Staatsoper, left Berlin it would be "the end of the Jewish mess" in the city. The young conductor denied the remarks and said it was an attempt to end his career as musical director of the Deutsche Oper.

"I have never said anything. I have to repeat that all the time. My conscience is clear. I never said these things," he said later. "Whoever accuses you has to produce the proof. I don't have to prove my innocence."

Thielemann was born in Berlin in 1959 and studied piano, violin and viola before deciding to become a conductor. As a teenager he became the assistant to septuagenarian Herbert von Karajan, a position that earned him the title "the young Karajan".

Another nickname that has stuck is "Superprussian", because of his severe military haircut, his love of the German repertoire and the portrait of Frederick the Great he keeps in his workroom as "a model of discipline and duty".

"If you had a Russian conductor and he conducted Russian works, you wouldn't say a word. Why do people say a word when a German conductor conducts German works?" he said last year.

The great and good of German society descended on Bayreuth last week to hear him conduct the premiere of Tannhäuser, directed by Frenchman Philippe Arlaud. Few in the cast and orchestra were surprised by the energetic booing from the audience. Christian Thielemann stayed away from the press conference, leaving Mr Arlaud alone to defend his staging as a "victory over barbarism". The critics didn't agree. Die Welt newspaper declared that Arlaud had "reduced Bayreuth from the centre of all things Wagner to a scrapyard of aesthetic kitsch theatre". The production was "derivative", the singers "shrill and indifferent".

Artistic director Wolfgang Wagner is used to bad reviews. He is hoping he will still be around in 2006 for the new production of Der Ring des Nibelungen, staged by the Danish film director Lars von Trier, whose musical film Dancer in the Dark won the Palme D'Or at Cannes.

The anti-Semitism that has overshadowed Bayreuth in the past is recalled this year with a new biography of Winifred Wagner, the conductor's daughter-in-law, who led the festival during the Nazi era.

Winifred Williams was 17 when she married Richard Wagner's son Siegfried, a man 28 years her senior, in 1915. After his death in 1930, she became artistic director and regularly welcomed Adolf Hitler into her household and to the festival. She appeared regularly in public at the side of the man she nicknamed "Wolf", and their close friendship earned her the title "Hitler's girlfriend".

The two first met in the 1920s and kept in contact during Hitler's time in prison in Munich. "I sent him packages of stationery while he was in prison which made people say that I gave Hitler the paper on which he wrote Mein Kampf," she said later.

She was removed as festival director after the war because of her staunch belief in the dictator, whom she believed was driven insane by poisonous injections from his physician, Theodor Morell.

"I say now what I said then, that he was a good, decent person. He was my friend," she said in a 1975 documentary film. "If Hitler were to come in the door today, I would be as happy and glad to see him and have him here as I always was."

Her reputation as an unreconstructed Nazi has been rehabilitated somewhat by a new biography by Viennese historian Birgitte Harmann, which draws on previously unpublished letters and papers. The letters show she intervened on many occasions to prevent Jewish, Communist and homosexual friends from being sent to concentration camps.

Other letters express Wagner's disgust at Hitler's anti-Semitic policies, and show that a distance grew between the friends during the war years.

After Nazi supporters spat at some Jewish artists at Bayreuth she fired off a letter to the dictator: "It is a disgrace that these honourable men should be denigrated by such rabid individuals. These Jews have earned a right to Bayreuth through their life's work."

Ms Harmann uncovered dozens of cases where, she says, Wagner intervened "spontaneously, automatically and with a great deal of human sympathy". Nevertheless she also uncovered plenty of fresh evidence of Wagner's Nazi beliefs, which tarnished her reputation until her death in 1980.