Prosecutors said they had launched an investigation into Joerg Tauss because there was "an initial suspicion" of the existence of incriminating pictorial material. However, the spokesman added that Tauss could be "completely innocent."

The politician, a member of the Social Democratic Party, said he could not understand why the searches of his offices in Berlin and Karlsruhe had taken place, but was not perturbed about the outcome.

"I have been concerned with the scene for years," Tauss said. He said he could not say whether this might an act of revenge.

"I am certain that we are going to clear up these accusations," he told German TV news channel ntv.

As the SPD's media expert, part of Tauss' job was to fight online child pornography.

Social Democratic Party heads said the accusations needed to be addressed calmly.

"This needs to be cleared up," said Ute Vogt, the chairwoman of Tauss's regional party association in southwestern Germany. "Until then we must presume that he is innocent."

Tauss has been subject to unfounded accusations in the past. Berlin's Tagesspiegel newspaper reported that he was accused of tax evasion two years ago after an anonymous complaint was filed. The allegations were not found to have any basis.