A man employed by Germany’s foreign intelligence agency (BND) has been arrested on suspicion of spying for the US. The espionage swoop is the latest of a series of embarrassing intelligence scandals straining ties between the two countries.

A 31-year-old German man was been arrested Wednesday on suspicion of being a foreign spy, according to a statement released by the German Federal Prosecutors Office.

On Friday, German authorities summoned the US ambassador in Berlin over the arrest of the alleged spy.

Two politicians with knowledge of the affair told Reuters on Friday that the unnamed man has admitted passing on details to a US contact about a special German parliamentary committee into National Security Agency (NSA) spying activities in Germany, which were revealed by former US intelligence contractor Edward Snowden.

Snowden said that the NSA and its British counterpart GCHQ eavesdropped on a number of European leaders’ phone calls, including those of German Chancellor Angela Merkel.

Both lawmakers are part of the nine member parliamentary control committee, which oversees the activities of the BND.

“The matter is serious, that is very clear,” a German government spokesman told the newspaper Frankfurter Allgemeine Zeitung.

The German tabloid Bild reported that the man had passed the Americans 218 secret documents in exchange for € 25,000 ($34,100) and has been a double agent for them for two years. The man allegedly met his contact in Austria and passed on the secret documents on a USB stick.

Der Spiegel magazine reported that he had confessed to passing on details about the NSA inquiry to a US contact in return for money.

There is also some uncertainty about what position he held in the BND. Earlier reports in Der Speigel that he worked in the mail room have now been discounted and Die Welt newspaper has alleged that in fact he was in close contact with Gerhard Schindler, the head of the BND.

One of the politicians on the committee also appeared to down play the man’s importance within the BND.

“This was a man who had no direct contact with the investigative committee. He was not a top agent," one of the politicians told Reuters.

He added that the man had offered his services to the US voluntarily.

But the Suddeutsche Zeitung newspaper alleged that the man had originally been suspected of spying for the Russians only to admit that he was working for the Americans.

As the parliamentary enquiry is confidential, it is not clear exactly what information the man is suspected of passing on the US.

But the MPs involved wanted to invite Edward Snowden to Germany to testify, although this was blocked by Chancellor Merkel in case Washington demanded his extradition.

MPs also offered to go to Moscow where Edward Snowden has political asylum, but the US fugitive refused to see them there.

However, two other whistleblowers and former NSA employees did testify. Thomas Drake claimed that the two agencies cooperate so closely that the BND is an “appendage”to the NSA.

Germany is sensitive to surveillance issues because of abuses by the Nazis and by the East German Stasi. After Snowden’s revelations Berlin suggested a no-spy arrangement between the US and its close allies, but Washington refused.

German media have said that if the case against the man is proven “it will be the biggest scandal involving a German-American double agent since the war.”

Last week Germany announced that it has ended a contract with Verizon, the US broadband and telecom company, because of security concerns about its systems, in the first example of Snowden’s revelations having commercial repercussions.