Is Germany a racist country? That is what a new documentary, Black on White, is trying to find out. Its findings are shocking. But, as Damien McGuinness reports, the filmmaker himself has been criticized by black Germans for his methods.
For more than a year, journalist Gunter Wallraff travelled across Germany wearing a dark-haired curly wig and with his white skin painted black.
Equipped with a secret camera, and calling himself Kwami Ogonno, he went to predominantly white areas to see how a black man with a foreign accent is treated.
The experience, he said, was even more depressing that he had expected.
"I hadn't known what we would discover, and had thought maybe the story will be, what a tolerant and accepting country we have become," said Mr Wallraff after a screening of the film Black on White in Berlin. "Unfortunately I was wrong."
He was almost beaten up by neo-Nazis after a football match in eastern Germany. And outside a small-town nightclub was told by a skinhead: "Europe for whites, Africa for apes."
But the film's most disturbing aspect is not the well-known racism of right-wing extremists, but rather the secretly-filmed reactions of everyday people - the landlady who says she could not possibly rent out a flat to a black person, or the shop owner who will not let "Kwami" try on an expensive watch, but willingly hands over the same watch to the next customer who is white.
For black people in certain parts of Germany such experiences are commonplace, believes Sven Mekarides, general secretary of the Africa Council in Berlin.
Mr Mekarides left his native Cameroon in 1991 and came to study in a small town in eastern Germany.
He says he and his fellow African students experienced racist attacks and abuse every day.
They were spat at, shouted at and beer bottles were thrown at them.
The worst attack took place in the eastern Berlin district of Lichtenberg in 2004, when Mr Mekarides and his girlfriend were surrounded by seven young men armed with knives.
"We soon realized that it was dangerous to travel in groups of less than three people. And we would never let any of the women go anywhere without accompanying them," he said in a Berlin cafe.
Since then, he said, the situation has not got much better.
According to the Amadeu Antonio foundation there have been 138 racially-motivated murders in Germany since 1990. And last year police registered 140 race attacks in Berlin.
"Those are only the most extreme cases the police know about," said Mr Mekarides.
"Every day we get calls from black people who have been falsely accused of stealing something or insulted on the street."
Clown in a carnival?
Although Mr Mekarides welcomes the discussion about racism the film has sparked off, he believes the filmmaker's exaggerated disguise confirms Europeans' worst stereotypes of an African.
"He just doesn't look like an African," said Mr Mekarides. "The wig, the make-up and the brightly-coloured shirt are all so over the top, he looks like he's a clown in a carnival.
"After he has washed his skin, he can forget the problem. But black people have this problem every day."
Some German newspaper commentators have accused the filmmaker himself of racism for acting out such a negative stereotype of a black person. The character of Kwami speaks broken German and is childlike in his ignorance of dangerous situations.
Anti-racism pressure groups, meanwhile, have complained that the filmmaker is paternally speaking for black people, rather than with them. Why did he not simply film the experiences of real black people?
"It was crucial that I take on these dangers myself," countered Mr Wallraff. "There's no way that I could delegate this role to someone else.
"I've been accused of being racist. But just imagine if I'd sent a black person into situations that I wasn't prepared to go into myself."
Torture and prison
With a celebrated 40-year career of unearthing social injustice, it is impossible to doubt Gunter Wallraff's motivations.
In one assignment he went undercover as an anti-government protestor in 1970s Greece and was tortured and imprisoned.
The film has won praise for starting a debate about racism in Germany. After a Q&A session with Mr Wallraff in a Berlin cinema, one young black woman said the film was "interesting, helpful and needed for Germany".
She said: "I've lived here all my life, and this is the first time I've ever seen an audience like this discussing this issue."
Racism is viewed as unacceptable by mainstream German society, and many urban areas pride themselves on a multi-cultural tolerant atmosphere.
But there do still exist so-called "no-go areas" - particularly in rural eastern Germany - which anti-racism activists advise non-white people to avoid.
Gunter Wallraff's film has already done a lot to spark discussion about racism. With an ageing population, Germany is now having to come to terms with being a country of immigration.
Clearly the debate is just beginning.