Officials in Berlin expressed outrage Sunday over remarks by Italy's former premier Silvio Berlusconi claiming that Germans denied the existence of Nazi concentration camps.

The disgraced billionaire made the provocative allegation Saturday during a campaign rally on behalf of his centre-right party for European elections in May.

Ralf Stegner, deputy head of the Social Democrats, partners in power with Chancellor Angela Merkel's conservatives, called on the European People's Party (EPP) -- the umbrella group to which Berlusconi's Forza Italia party belongs -- to condemn his claim.

"The EPP must confront this intolerable slur against all German citizens with absolute decisiveness," he was quoted by the daily Sueddeutsche Zeitung as saying.

"Those who silently tolerate such remarks in their own party family endanger the solidarity of democrats."

Manuela Schwesig, Germany's family affairs minister, fired back almost immediately on Twitter late Saturday, calling Berlusconi's comments "unspeakable" and a direct attack on the German chief of the European Parliament, Martin Schulz, the centre-left candidate in the race to lead the EU Commission.

Schulz himself, in an interview with Der Spiegel news magazine conducted before Berlusconi made his remarks, accused Forza Italia of whipping up anti-German sentiment with its slogan "More Italy, Less Germany".

"Germany is a land that has shown a lot of solidarity and that is why such posters are outrageous," he said.

The German government told AFP it had no comment on the matter.

Berlusconi had been expanding on comments he made in 2003 when he jokingly offered Schulz a part in a film as a "kapo", a concentration camp inmate tasked with overseeing other prisoners.

The media magnate bridled while in power at German demands for the eurozone's debt-mired countries to sharply curb their spending as a condition for European bailouts.