European Union officials feel the US had dealt Europe a "slap in the face", a member of the European Parliament said on Tuesday, following claims the US National Security Agency bugged EU offices and hacked into its computer network.
"The EU has to respond pretty robustly to the Americans' activities. It's clear the US have been involved in spying into EU institutions and activities. What I think we should be insisting on is that the US issues a clear apology, and a commitment to end this activity," David Martin, a member of the European Parliament's International Trade Committee, said on Tuesday.
European leaders warned on Monday that the alleged bugging could derail major trade talks, with France's President Francois Hollande saying that Europe would hold off on any negotiations until it was sure the US spying had ended.
"A lot of people feel this is a slap in the face.The EU has made big efforts to get these talks underway and they feel extremely let down by the Americans," Martin said.
"I think it does weaken trust. There is no point running away from it. It does undermine confidence in each other's negotiating position and trust."
Reports published over the weekend by The Guardian newspaper and Germany's Der Spiegel, claimed the National Security Agency (NSA) had run an extensive program to spy on the EU representative's office in Washington as well as the EU office to the United Nations in New York. Der Spiegel also reported one spying operation had targeted an office that housed the EU Council of Ministers in Brussels.
Another member of the European Parliament told CNBC that the U.S.-EU trade talks are now likely to be delayed, adding that when they do occur, the spying allegations would be the "elephant in the room".
"We would need some major show of goodwill I think from the United States," Sharon Bowles, the chair of the European Parliament's Economic and Monetary Affairs Committee said on Tuesday.
"It's just going to be there in the back of your mind; did they listen in? Do they have an unfair advantage? Do they know all our strategies? Even though I'm sure they'll tell us that the bugging is all to do with security."
Bowles added that the U.S. spying allegations appeared to be part of a "recurring theme."
"Just saying 'Whoops! Sorry and it won't happen again', is not really going to be enough," she said.
(Read More: US Bugged EU Offices, Hacked Into Its Computers)
Earlier in the week, Germany's foreign ministry summoned the US Ambassador to seek clarification. Plus, German Chancellor Angela Merkel will also discuss the issue with President Barack Obama, her spokesman said on Monday.
"We are no longer in the Cold War," a spokesperson for Angela Merkel said on Monday. "If it is confirmed that diplomatic representations of the European Union and individual European countries have been spied upon, we will clearly say that bugging friends is unacceptable."
But the most strongly worded statement came from Hollande, who said that the behavior was unacceptable and should that it should cease immediately.
Bowles told CNBC that it wasn't surprising that it was the French calling for the delay in EU-US talks as they were the most reluctant even before the allegations surfaced.
Fears that the pact could open up fiercer competition in areas such as agricultural goods and the film industry have previously been discussed, with France threatening to veto certain sectors from any agreement.
"There's been some reluctance about these talks in France anyway because of the culture and film issue. So it's not surprising that they're the ones that call for a delay," Bowles said.