The transfer of financial data from Europe to the US 'to fight terrorism' may be unjustified, according to EU Information Society Commissioner Viviane Reding.
In a speech marking Data Protection Day, she said that the amount of financial data being transferred to the US had 'considerable privacy-invading potential'.
"I remain to be convinced that all these SWIFT transfers are necessary, proportionate and effective to fight terrorism. I will be looking into this very closely in the coming weeks," she warned.
"I want to make sure that our EU legislation and international agreements are based on evidence rather than on emotional responses to the latest scare."
European banks have been providing financial information to the US via SWIFT - the Society for Worldwide Interbank Financial Telecommunication - since at least 2006.
Known as the Terrorist Finance Tracking Program, the initiative forms part of the Bush administration's 'War on Terrorism'.
Redding also said she was looking for greater privacy controls in behavioural advertising, as data was routinely being collected and used without users' consent or even knowledge.
"Users are not always aware that they are being tracked whenever browsing the internet. We have launched an infringement procedure in the so-called Phorm case, alerted by worried citizens of the UK," she said. "For me it is clear that without the prior informed consent of citizens their data cannot be used."