A report by the U.S. National Security Agency that suggests it spied on EU offices has infuriated European officials.

The European Union has warned that if the report is accurate it will have tremendous and wide reaching repercussions. Martin Schulz, the President of the European Parliament, said he was deeply worried and shocked about the allegations and has stressed that if the allegations prove to be true it would have a severe impact on EU-US relations. Acting on behalf of the European Parliament, Mr Schulz has demanded full clarification and is seeking further information from the U.S. authorities on these allegations.

Sabine Leutheusser-Schnarrenberger, the German Justice Minister, said that if the accusations were true that would be reminiscent of the Cold War. The German minister has also asked for an immediate explanation from the United States.

Citing information from secret documents obtained by former NSA employee Edward Snowden, the German newsmagazine Der Spiegel reported that several U.S. spying operations targeted EU leaders.

Der Spiegel says the documents from Snowden describe how the National Security Agency bugged EU officials’ Washington and New York offices and conducted an ‘electronic eavesdropping operation’ that tapped into an EU building in Brussels.

Ben Rhodes, the deputy national security adviser for strategic operations in the White House, said he had not seen the report and would not comment on unauthorised disclosures of intelligence programs. Mr Rhodes did say, though, that the United States does work very closely with its European partners and has very close intelligence relationships with Europe.

Michael Hayden, a former director of the CIA and NSA, whilst having been out of government for some five years, said he didn’t know whether the report was true. Mr Hayden was clear, however, on a number of points confirming that the United States does conduct espionage and, that in relation to the US’s Fourth Amendment, which protects the privacy of Americans, does not amount to an international treaty. The former CIA director was also reticent about Europeans looking first to what their own governments are doing in respect to international espionage.

Der Spiegel’s report comes at a particularly sensitive time. The first round of negotiations for a trans-Atlantic trade agreement between the United States and the European Union are set to start next month in Washington.