German Justice Minister Sabine Leutheusser-Schnarrenberger used a newspaper interview to demand that the BND (Bundesnachrichtendienst) intelligence service provide a full explanation after it admitted to passing on massive amounts of so-called "metadata" to the US National Security Agency (NSA).

"The BND must finally put the facts on the table," Leutheusser-Schnarrenberger said in comments published in Monday's edition of the Münchner Merkur newspaper.

"If it is true that the BND made itself available as a tool for the NSA in the mass gathering of data, than something urgently needs to be done," she added.

This came after the BND confirmed the Spiegel Online story, which cited documents it said it had received from former NSA subcontractor Edward Snowden. It said the NSA had received around 500 pieces of metadata through such channels last December alone.

A BND spokesman told the DPA news agency on Saturday, though, that any personal information had been filtered out of the data before it was passed on to the Americans. He also said any activities the agency had carried out were in complete compliance with German laws, including the one that regulates the BND.

Deputy government spokesperson Georg Streiter also defended the intelligence activities, adding that the BND had only forwarded two sets of data in 2012, and both were about the same individual.

"German [intelligence] offices are obeying data protection laws," said Steiger.

The latest revelations about the alleged mass surveillance of Germans' internet usage and telecommunications by the NSA comes just weeks before the country is to go to the polls in a federal election on September 22.

Campaign issue

The opposition has repeatedly taken the opportunity to attack Chancellor Angela Merkel's government for not pushing their American counterparts forcefully enough for answers.

On Sunday, Merkel's Social Democrat challenger, Peer Steinbrück, used a major television interview to attack the chancellor on the issue. He called on the chancellor to demand a written guarantee from the Americans that any activities they carry out here comply with German law, do not harm German interests, and do not include industrial espionage.

In the interview with public broadcaster ZDF, Steinbrück also defended his party's strategy of trying to make the snooping affair into a campaign issue.

He said he regarded it as acceptable for the Social Democrats to "point out, with a touch of humor, a touch of irony, that Mrs. Merkel is taking a wait-and-see attitude, while at the same time there are millions of cases of basic rights being breached." He also said it raised the question about whether Germany is actually master of its own house.

So far though, there seems to be little indication that the issue is having much of an impact on the voters. An opinion poll published by public broadcaster ARD gave Merkel's conservatives a lead of 16 percentage points over the Social Democrats.

pfd/hc (Reuters, dpa, AFP)