Vice Chancellor Sigmar Gabriel was responding to claims that the BND had helped the US National Security Agency (NSA) spy on German firms.

Last week, a leaked BND report suggested it had monitored French and EU targets for the NSA.

Mrs Merkel defended the BND, in her first public comments on the scandal.

Its first priority was to ensure the safety of Germans, she said on Monday, and the government would do all it could to enable the agency to carry out its role.

"This ability to carry out its duties in the face of international terrorism threats is done in co-operation with other intelligence agencies, and that includes first and foremost the NSA."

While her office was prepared to respond to all questions, she said "striking the right balance is my job".

But Mr Gabriel, the leader of the centre-left SPD, increased the political pressure on the chancellor by calling for a "thorough inquiry".

He said a list of "selectors" - mobile phone numbers and IP addresses - handed by the NSA to German intelligence should be made available to parliamentary committees investigating the affair.

He had twice asked the chancellor if German companies had been targeted and twice she had denied it, he said, adding that he had no reason to doubt she had answered correctly.

SPD deputy chairman Ralf Stegner told German newspaper Suddeutsche Zeitung that "the game" of saying the latest revelations were nothing to do with the chancellor was up. Her chief of staff, Peter Altmeier, should give evidence to MPs, he said.

`Treason`

The BND has worked with the US for years, but it is now clear that the targets went far beyond potential terrorist threats.
Its monitoring station at Bad Aibling was reportedly used to spy on the French foreign ministry and presidential palace as well as the European Commission and Airbus group.

The head of German intelligence, Gerhard Schindler, rejected as "totally absurd" a suggestion by opposition politicians that the BND committed treason by helping the US.
"The BND isn`t a compliant tool of the United States," he said.

Interior Minister Thomas de Maiziere, who like Mr Schindler has come under pressure to resign over the affair, is due to give evidence to the Bundestag`s intelligence committee on Wednesday.

When Mrs Merkel herself was the target of US spying in 2013, she admonished the Americans with the words: "Spying between friends, that`s just not done."

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