Uwe Luthardt was a senior member of the NPD but quit to inform on the party which Germany tried unsuccessfully to ban several years ago.
He told of weapons stores and how members greet each other with "Heil Hitler" salutes, sing the banned songs of the Third Reich and relish the idea of a new Holocaust against the Jews.
Last year neo-Nazi attacks in Germany reached an all-time high and authorities are battling to stop youngsters from being attracted to the politics of the right - particularly now that Germany is in a deep recession and jobs are being lost by the thousands every day.
Luthardt, a former board member of the party, said he was threatened that he could "disappear" if he informed on its inner workings.
"Someone who just quits usually gets a lot of problems, and can find himself waking up in intensive care," he said.
"It wasn't really my world. When you went along to evening meetings, you saw all the shaven heads, and a black sun or other Nazi symbols tattooed on arms. They usually just boozed or were abusive. If there's no opponent around, they just fight among themselves.
"Many have an IQ close to my shoe size. Most of them are simply failures: failed pupils, people who dropped out of school or their apprenticeships, alcoholics that can't find a foothold anywhere else, thugs. But every local organisation has three to five men who don't have criminal records. They're the ones sent to face the press or man information stands.
"I joined because I wanted to do something for Germany, I wasn't interest in a Greater Germany. And suddenly everyone was saying we'll take back Silesia in Poland and then we'll give the communists a thrashing."
He said old Nazis living in South America still donate to the party and other funds come from the staging of skinhead-music concerts.
He went on: "The simple aim is the restoration of the Reich in which a new storm trooper organisation takes revenge on anyone who disagrees with them.
"In Jena in East Germany in the NPD HQ there are a load of SS pictures in the cellar. And there's a room with weapons.
"'Let's kick out all the foreigners, then the Germans will have jobs again' - that's the basic concept the NPD talks about. They only refer to freight trains when no one from outside is listening." That is a chilling reference to the murder of the six million Jews of Europe during the Third Reich, most of whom were transported to extermination centres in railway cattle cars.
"They want the Jews and the foreigners to be transported away once more once they've taken over the country again. Internally there's very plain speaking. And the singing of the Horst Wessel song - the anthem of the original Nazi party - is also very popular.
"But there are internal documents which clearly state how everyone should behave in public. Anything to do with the Third Reich is especially sensitive.
"The dream is of the German Reich. They're totally convinced that they'll win an election one day and that things will really get going.
Everyone can imagine what would happen then."
