Now it's personal: Claims US tapped Merkel's phone set off firestorm

As the extent of US spying practices has emerged over the past six months, America's longtime European allies have publicly protested – even as they expressed little surprise behind the scenes.

But the tone on the Continent has changed markedly this week. On Monday, a report in France's Le Monde Monday alleged that the US had accessed massive amounts of French telephone data. And yesterday, the German government said it had information that Chancellor Angela Merkel's mobile phone might have been bugged.

Both countries summoned the US's ambassadors to answer to the accusations, as anger mounted in a way that some say could profoundly shift the allies' relationships, most notably in the ambit of data privacy.

“Enough is enough,” is how one European official described the mood to the BBC, as the European Union gathers for a two-day summit that promises to be dominated by the NSA scandal.

While European politicians were dismayed at the initial allegations of American surveillance of metadata, revealed by former NSA contractor Edward Snowden, the mood has darkened considerably since it was alleged that the US is directly spying on embassies and individuals in Europe.

“The [former] can be seen as [part of] the war on terror. They are not directly listening to what everyone is saying ... but on who is speaking to whom,” says Henning Riecke, head of the US transatlantic program at the German Council on Foreign Relations in Berlin. “But the other is traditional espionage for economic and political gain.”

Thursday's Süddeutscher Zeitung in Germany, in front-page commentary, likened the alleged listening in on Merkel's phone as an attack on “her political heart.”

And German Defense Minister Thomas de Maizière, on ARD television, said that "We can't simply return to business as usual. There are allegations in France too."

US President Obama spoke with both Chancellor Merkel and French President François Hollande after Le Monde's allegations – some of which the US denies – involving 70.3 million pieces of telephone data recorded by the NSA in a little over a month's time, from December 2012 to January 2013.

Subsequently, the White House said in a statement that “The President assured the Chancellor that the United States is not monitoring and will not monitor the communications of Chancellor Merkel."

But that has not tempered dismay from Germany, along with France, both of which will be on display at the two-day EU summit, which begins Thursday afternoon in Brussels.

Heads of EU institutions have, in many ways, been harder on the US in rhetoric than the individual member states have. The European commissioner for justice and fundamental rights, Viviane Reding, said when American spying on European partners was alleged this summer: "Partners do not spy on each other." The European parliament, meanwhile, has led calls for tougher EU rules on data privacy.

Fredrik Erixon, the director of the European Center for International Political Economy (ECIPE) in Brussels, says this is in part because member states have security apparatuses and know the kind of espionage that is regularly carried out – unlike the EU. “Member states of the EU have taken a fairly soft stance, while European institutions have taken a hard one,” he says.

That might change now with leaders joining forces to condemn the US and demand clear answers on the extent of what they are listening to and why.

When allegations of US spying on Germany meta data came out this summer, Merkel wasn't blunt with the US is demanding an apology, says Dr. Riecke. But as leaks mount, Germany has become more aggressive. The US ambassador to Germany, John Emerson, was to meet Thursday with German Foreign Minister Guido Westerwelle over phone tapping claims. The issue is particularly sensitive in Germany, where the Stasi police in the former East Germany – where Merkel is from – widely spied on citizens.

“The government has to react harshly now," says Riecke.