Jörg Tauss, a Social Democrat in the grand coalition, quit as his party's parliamentary media affairs and education spokesman and as the regional party general secretary for Baden-Württemberg state after police raided his Berlin and Karlsruhe offices.
Mr Tauss was stripped of his parliamentary immunity on Thursday when news of the raid broke. He said he had resigned, six months before Germany's general election in September, "to avert damage to my party and my parliamentary group". He has campaigned against online child pornography and said he was "absolutely sure" he could be quickly cleared of the accusations.
Prosecutors rejected Mr Tauss's claims that the investigation was a result of his campaign against child pornography. A prosecutor with knowledge of the case said officers had found incriminating material in Mr Tauss's Berlin apartment which demanded an explanation. "It clearly has no connection with his activities as an MP."
Reports said the investigation had been launched after prosecutors in the northern city of Bremerhaven found Mr Tauss's phone numbers and his Berlin address in the possession of a man already suspected of involvement in child pornography distribution.
Source: FOCUS Information Agency