The EU will investigate whether telecoms operators are providing fair internet access and might introduce stricter rules to protect consumers, EU Telecoms Commissioner Neelie Kroes said on Tuesday.

The comments underline a growing debate over net neutrality -- the principle that all internet traffic be treated equally -- with Europe adopting a more hands-off policy to date compared with U.S. regulators.

Internet providers say they should be free to manage their networks for the benefit of all users, but content providers are worried about disruption of access and anti-competitive behavior.

The Commission has asked the Body of European Regulators for Electronic Communications (BEREC) to undertake a rigorous fact-finding exercise on issues crucial to ensuring an open and neutral Internet, Kroes said in a statement.

She cited possible barriers including changing operators, blocking or throttling internet traffic in areas such as voice over internet services, levels of transparency and quality of service.

If BEREC's findings and other feedback indicate outstanding problems, the Commission will assess the need for more stringent measures, Kroes said.

The comments indicated a shift in Kroes' position, after she said last year that strong competition in broadband markets may allow a more relaxed regulatory approach to net neutrality issues.

The European Commission plans to publish the results of BEREC's investigation by the end of the year.

CONSUMER POWER Lobbying group Cable Europe, whose members include Liberty Global, Virgin Media Inc and Kabel BW, said there were enough safeguards in the system to deter providers from favoring their own services without the need for more rules.

Individual companies that behave anti-competitively can be sanctioned through current provisions in telecoms legislation and competition rules, Cable Europe's managing director, Caroline Van Weede, said in a statement.

But, in the end, the sanction of the customer is most swift, given countless social networking tools, blogs and fast-moving web publications.

The European Telecommunications Network Operators' Association, whose members include Telefonica, Orange and Telecom Italia, pointed to the risks of more rules in the sector.

In highly competitive markets for fixed and mobile broadband, any further regulation that would restrict traffic management and service differentiation would undermine Europe's digital economy and hamper innovation, Luigi Gambardella, ETNO's chairman, said in a statement.

Analysts said mobile operators fear the threat to their core business from Google, Skype or Facebook, which offer practically free voice communications and messaging services.

U.S. communications regulators adopted rules in December last year that banned high-speed Internet service providers from blocking lawful traffic but allowed them to reasonably manage their networks.

(Editing by Charlie Dunmore and Will Waterman)

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