Many individual subscribers are unaware of the scale and implications of these developments

Frits Bolkestein, EU Commissioner

The Commission - the European Union's executive body - said it wants to encourage the development of internet services, while ensuring individual privacy rights are protected.

The Internal Market Commissioner, Frits Bolkestein, said: "current technology allows a single cyber-marketing company to send half a billion personalised ad mails via the world-wide web every day."

But "many individual subscribers are unaware of the scale and implications of these developments," he said.

The Commission said it had launched the study as part of an ongoing effort "to ensure that the development of the Internet and e-commerce does not undermine Europe's rules on internet privacy and data protection."

In a statement, it said it was up to internet companies to answer such concerns.

"Unless consumers feel their privacy is adequately protected, the online services that are so important to wealth and job creation in Europe are unlikely to flourish."