The decision coincides with suggestions that a deal had been struck between the Havas shareholder Vincent Bolloré and Telefónica’s chairman, César Alierta.
A spokesman for Telefónica confirmed that the initial selection of ZenithOptimedia in July had been usurped by a "global strategic appointment of Havas Group" that will include media planning and buying.
The spokesman would not comment on whether Bolloré had a role to play, but said that the decision to appoint Havas globally "had always been an ongoing consideration".
Paul Bainsfair, the IPA’s director-general, said: "The IPA New Business and Marketing Group would like to express concern over the reported outcome of this process… The impact of poor pitch practice on agencies can be far more crippling than many clients appreciate."
In the UK, Telefónica’s O2 is one of ZenithOptimedia’s longest-standing clients, with roots stretching back to 1991.