Germany's intelligence agency, the BND, has denied that mobile phone data it sends to the NSA could be used in drone attacks carried out in Afghanistan and Pakistan.

Chancellery minister Ronald Pofalla told a closed parliamentary committee that GSM data, which the BND has admitted sending to other foreign secret services, was not specific enough to pinpoint exact locations, according to Left Party politician and committee member, Steffen Bockhahn.

Following the meeting on Monday, Pofalla, who is responsible for the BND, told reporters the NSA and the British intelligence services, GCHQ, had sent written assurances they were abiding by German law.

The BND has faced widespread criticism in Germany since it was revealed it had collaborated with the NSA and GCHQ by sending hundreds of millions of pieces of metadata every month.

Over the weekend, it was reported that mobile phone information sent to the NSA could have been used in the targeting of a terrorist group, which also resulted in the death of a German citizen as part of a drone attack in Waziristan on the border of Afghanistan and Pakistan in October 2010.

Germany's federal state prosecutor ruled in July that the death of 20-year-old Bünyamin E. was legal under international law because he was "not a civilian protected by international human rights law, but a member of an organised armed group".

The BND has denied it sent Bünyamin E.'s phone data to the NSA, but said any information sent to foreign intelligence agencies was done so with the condition that the data must not be used as a "basis or reason for unreasonable measures", such as torture or for the "passing of a death sentence".

However, Bockhahn, said it is impossible to know what foreign agencies are doing with data passed on by the BND.

"You can't control [other intelligence agencies] if they take the information and use it with their own intelligence…and then use drones," he said.

"Intelligence agencies are impossible to control and it is impossible to know if they accept foreign law and my feeling is they don't. Indirectly, Germany is responsible for the drones."

Human rights lawyer Eberhard Schultz said if Germany's intelligence agency was responsible for sending information used in drone attacks resulting in deaths, it would violate Germany's international criminal law and the German criminal code.

"That is an aid to war crimes and to murder and the murder is not justified because there was no trial and there is no chance to defend oneself," he said.

Experts disputed that the information could not be used in the targeting of terrorism suspects by intelligence agencies, at least in some cases.

"They are right that in a lot of cases that data is not enough to localise and target someone, but in some cases it is enough to locate a person within the cell of the mobile network and that's the problem," said Hannes Federrath, a professor of information technology and security at Hamburg University.

"Even if in 90% of the cases it's not possible, and in 10% of the cases it is possible someone can be targeted, then it is an illegal situation, if data is transmitted to another secret service."

Meanwhile, anti-drone campaigners said if data collected by German authorities was used to target people using drones, it could "not be accepted".

"If data from Germans, no matter from who, the foreign state secret services or any other services from Germany, was used for such an aim, this is something that has to be brought to court and cleared up," said Michael Ebeling, a coordinator at the German Drone Campaign, an umbrella organisation for groups fighting against the use of drones.