BRUSSELS (Reuters) - EU antitrust regulators have decided to expand their investigation of Orange's (>> ORANGE SA) planned 3.4 billion euro (2.6 billion pounds) bid for broadband specialist Jazztel (>> Jazztel PLC) in Spain.

Orange, France's largest telecom group, wants to boost its strength in Spain where it competes with market leader Telefonica (>> Telefonica SA) and Vodafone (>> Vodafone Group plc).

The European Commission said in a statement on Thursday that it had opened an in-depth investigation into the plan, giving it 90 working days until April 24 to take a decision.

Orange said in a separate statement that is was confident the deal would still be approved and wants to close it during the first half of 2015.

Buying Jazztel would give Orange the ability to sell broadband and mobile bundles, which are becoming increasingly popular in Spain like elsewhere in Europe. It would add 1.5 million broadband subscribers to Orange's client base.

The Commission said that the combined Orange Spain and Jazztel would not be in a dominant position, but it had concerns that the proposed deal would lead to a significant loss of competition for fixed Internet access and fixed-mobile multiple play offers, potentially resulting in price increases.

The Commission said that possible concessions Orange submitted on Nov. 13 were insufficient to dispel its concerns.

The Spanish telecoms market has seen a wave of consolidation in recent months as tough competition and falling prices hit operators. The most notable deal was Vodafone's 7.2 billion euro takeover of Spanish cable operator Ono in March.

(Reporting By Philip Blenkinsop; editing by Adrian Croft and Elaine Hardcastle)

Stocks treated in this article : ORANGE SA, Telefonica SA, Jazztel PLC, Vodafone Group plc