European Union ambassadors met Thursday in Brussels ahead of talks due to begin Monday on a U.S.-EU free trade deal, CNN reported.
Much of Thursday's discussions focused on allegations made by National Security Agency whistle-blower Edward Snowden that the United States spied on European diplomats.
The European Parliament then voted to conduct an in-depth inquiry into the U.S. surveillance programs, including PRISM, a statement from the European Parliament said.
European lawmakers also expressed "grave concern" similar surveillance programs are run by several EU member states, including the United Kingdom, Sweden, the Netherlands, Germany and Poland, the statement said.
Nonetheless, the European Commission said the U.S.-EU free trade talks will go ahead as planned.
"Whilst the beginning of EU-U.S. trade negotiation should not be affected, the EU side will make it clear that for such a comprehensive and ambitious negotiation to succeed, there needs to be confidence, transparency and clarity among the negotiating partners," it said in a statement.