EU antitrust regulators opened an in-depth investigation on Friday into a bid by Vivendi's Universal Music to buy EMI's recorded music unit for 1.1 billion pounds, saying the proposed deal could reduce competition to the detriment of consumers.

Universal decided not to offer concessions to the EU watchdog during its preliminary assessment of the deal, but would consider doing so in the second phase of the review, a person familiar with the matter told Reuters last week.

The European Commission said it was concerned about the combined entity's high market share, almost twice the size of its nearest rival in Europe, and increased market power.

The Commission needs to make sure that consumers continue to have access to a wide variety of music in different physical and digital formats at competitive conditions, EU Competition Commissioner Joaquin Almunia said in a statement.

The European Commission said it would now decide by August 8 whether to clear or block the deal.

EMI owner Citigroup took control of the record label, whose artists have included the Beatles, Queen and Coldplay, after its previous owner Guy Hands' buyout shop Terra Firma defaulted on loans owed to the investment bank.

The Commission has asked rivals and consumer groups whether the Universal deal, and a Sony-led <6758.T> plan to acquire EMI's music publishing business for $2.2 billion, will result in higher prices and also shut out competitors.

A questionnaire sent by the European Commission and seen by Reuters asked whether artists would be able to switch record labels easily and at a reasonable cost once the two deals were completed.

Both Universal and the Sony-led group were expected to argue that strong competition in the music business meant their acquisitions would not restrict competition and that online music distributors such as Apple and Amazon have more power in terms of pricing.

Impala, a lobbying group for independent music companies, has urged EU regulators to block both deals.

Rival Warner, which had also sought to buy EMI's recorded music, was expected to warn the Commission about the risks of an overly concentrated market.

(Editing by Philip Blenkinsop and Erica Billingham)