Allegations that the US used covert surveillance to target the French embassy in Washington DC as well as its envoy to the UN in New York have drawn an angry response from Paris.
Reacting to the reports for the first time on Monday French President François Hollande told Washington DC that the covert surveillance of its envoys must "stop immediately".
"We cannot accept this kind of behaviour between partners and allies,"Hollande told journalists during a visit to the northwestern city of Lorient. "We ask that this stop immediately ."
Hollande said "enough elements have already been gathered for us to ask for explanations" from Washington about the spying allegations.
In the latest documents leaked by the fugitive former CIA operative Edward Snowden to the Guardian newspaper it is claimed that the French embassy was one of 38 spying targets conducted by US intelligence services.
Attempts were apparently made to eavesdrop on the French, Italian and Greek embassies in Washington while Japan, Mexico, South Korea, India and Turkey were all named as subjects of operations in a 2010 document.
The revelations have sent minor tremors around Europe and provoked an angry response in Paris as well as Berlin and Brussels.
Reports in German weekly Der Spiegel on Monday that EU diplomatic missions were also put under secret surveillance have added more fuel to the fire and led to calls in France for talks over a landmark EU-US free trade deal to be binned.
"There can be no negotiations or transactions in all areas until we have obtained these guarantees, for France but also for all of the European Union, for all partners of the United States," Hollande said in an apparent reference to the sensitive talks.
"We know well that there are systems that have to be checked, especially to fight terrorism, but I don't think that it is in our embassies or in the European Union that this threat exists," he said.
And the French Minister of Foreign Trade Nicole Bricq said the upcoming talks on the new trade zone, due to begin next week, could be jeopardised.
"This is a topic that could affect relations between Europe and the United States," she told AFP.
"We must absolutely re-establish confidence… it will be difficult to conduct these extremely important negotiations," she said.
Hollande said he had asked Foreign Minister Laurent Fabius to get in touch with US Secretary of State John Kerry immediately "to get all the explanations and all the information."
On Sunday Hollande's Foreign Minister expressed his concern over the revelations.
“These facts, if confirmed, would be completely unacceptable,” Fabius said.
“We expect the American authorities to, as quickly as possible, allay the legitimate concerns raised by these media revelations,” he added.
One of the leaked US National Security Agency (NSA) files said that intelligence officials targeted embassies and UN missions by implanting bugs in electronic communications gear, tapping into cables and collecting communications using specialized antennae, according to a report on the Guardian's website on Sunday.
The operation against the French mission to the UN was dubbed 'Blackfoot' and the one against its Washington embassy was known as 'Wabash'.
France’s Justice Minister Christiane Taubira said: “It would be an act of unspeakable hostility if European institutions were indeed under the surveillance of the American secret service.”
The allegations have drawn condemnation not just from the government but from across the political spectrum in France.
Marine Le Pen, leader of the far-right National Front party said: “We can’t be the poodles of the United States.”
And her nemesis from the far-left, Jean-Luc Melenchon, called for EU-US free trade talks to be broken off in protest over the allegations.
“I demand an immediate halt in negotiations and I demand that France grant asylum to Edward Snowden who is a friend of Europe for unmasking this conspiracy,” he said.
The US said on Sunday it would respond to the EU via diplomatic channels over the bugging allegations.
"While we are not going to comment publicly on specific alleged intelligence activities, as a matter of policy we have made clear that the United States gathers foreign intelligence of the type gathered by all nations," said a statement from the office of the Director of National Intelligence in Washington.
The US authorities issued an arrest warrant this month for Snowden after he revealed details of NSA's so-called PRISM programme which collects and analyzes information from internet and phone users around the world, with access to data from Google, Yahoo! and other Internet firms.
Snowden remains in political limbo at Moscow's Sheremetyevo airport after flying in from Hong Kong last week, unable to fly on without legal travel documents or exit the airport without a Russian visa.