The Parliament's President and political group leaders formally confirmed the launch of the inquiry. MEPs also called for more protection for whistleblowers.
In the resolution, approved by 483 votes to 98 with 65 abstentions, MEPs express serious concern over PRISM and other surveillance programs, strongly condemn spying on EU representations and call on the US authorities to provide them with full information on these allegations without further delay.
Parliament also expressed grave concern about allegations that similar surveillance programs are run by several EU member states, such as the UK, Sweden, The Netherlands, Germany and Poland, and urges them to examine whether those programs are compatible with EU law.
The Civil Liberties Committee inquiry will gather information and evidence from both US and EU sources and present its conclusions in a resolution by the end of the year. It will assess the impact of the alleged surveillance activities on EU citizens' right to privacy and data protection, freedom of expression, the presumption of innocence and the right to an effective remedy.
MEPs involved in the inquiry will table recommendations to prevent similar cases in future and step up IT security in the EU institutions, bodies and agencies.
MEPs stress the need for "procedures allowing whistleblowers to unveil serious violations of fundamental rights" and the importance of providing such people with the protection they need, including at international level.
They also call on the European Commission, the Council of Ministers and EU countries to consider possible recourse to all levers at their disposal in negotiations with the US, including suspending the current air passenger and bank data deals (Passenger Name Record and Terrorist Finance Tracking Programme, respectively).
EU data protection standards should not be undermined as a result of the EU-US trade deal, warns the resolution, adding that it would be "unfortunate" if EU-US trade talks were to be affected by such allegations.
Parliament calls on EU countries to speed up their work on the whole data protection package and urges the Commission and the US authorities to resume negotiations on the data protection agreement without delay. The final deal must ensure that EU citizens' access to the US judicial system is equal to that enjoyed by US citizens, it adds.