The concerns came in the wake of German media reports that the country's foreign espionage agency, the BND, had helped the US National Security Agency (NSA) to spy on targets such as Europe's Airbus Group, the French presidency and the European Commission.
The German Sunday newspaper "Welt am Sonntag" reported that several foreign intelligence representatives had expressed concern to their German counterparts.
The BND currently cooperates with 451 intelligence services in 167 countries.
CSU politician Hans-Peter Uhl told "Welt am Sonntag" that the BND's reputation had been damaged. He said foreign intelligence services would be "very sensitive to the fact that information declared secret could end up in the public domain in Germany."
Who knew what?
Of particular interest is the extent to which the BND willingly cooperated as the NSA broadened its surveillance from potential terrorist threats to European officials and businesses - and what the Germany's federal government knew.
Germany's opposition has launched a fresh political attack on Angela Merkel's government, claiming that Merkel's cabinet had done nothing to stop its foreign intelligence service from spying for the United States.
US whistleblower Edward Snowden said in a comment published in the German media on Friday that mass surveillance was being used on a large scale - in part to aid industrial espionage.
"Massive surveillance is a reality. Industrial espionage is practiced, and the intelligence services are working beyond the control of the representatives of the people and of justice," Snowden told German weekly news magazine "Der Spiegel."
Request for search terms, addresses
Interior Minister Thomas de Maiziere denies he lied to parliament over the cooperation with the NSA.
To clear up the accusations, Germany's Social Democrats - the grand coalition partners of Merkel's Christian Democrats - have asked for a list of "selectors." These include IP addresses, search terms and names that the BND has been tracking on behalf of the NSA.
German media reported on Thursday that the BND has severely restricted cooperation with its US partner the NSA in the wake of the scandal. The German agency was reportedly only sharing phone and fax intercepts, and not internet data - unless a justification is provided. Justification is already required to share the telephone and fax data.
rc/gsw (AFP, AP, dpa, Reuters)