Mobile tariff cuts introduced by European Union regulators will leave a multi-billion-euro hole in the telecoms sector's investment budget, Telefonica's chief operating officer said on Monday.

On July 1, the EU implemented a series of cuts to mobile roaming tariffs for making a telephone call, sending a text message and reading emails.

Brussels also wishes to push through a drastic cut in termination charges for mobile calls.

Those two measures alone will cut investments by 6 billion euros ($8.57 billion), COO Julio Linares said during a European telecoms conference in the northern Spanish city of Santander.

As far as revenues are concerned, the cuts to roaming tariffs will have a impact of 6 billion euros and European operators will lose a further 34 billion from the decrease in call termination rates, Linares said.

The impact of changes to termination tariffs will be partly compensated by the fact that operators will pay less to access rivals' networks.

(Reporting by Robert Hetz; writing by Judy MacInnes; editing by John Stonestreet)