He returned to Italy in 1993, where he was the Personal Assistant to the President (Romano Prodi) of the Istituto per la Ricostruzione Industriale (IRI).

On 18 May 2006, Tononi joined the 2nd Cabinet of Romano Prodi, where he served as Treasury Undersecretary of the Ministry Of Economy and Finance (2006-2008), then headed by Tommaso Padoa-Schioppa.

[4] In 2007 Tononi was implicated in a scandal regarding the Italdel-Siemens merger in the mid 1990s,[5] In February 2007 the Treasury Police raided the Milan office of Goldman Sachs, where they removed a file called "MTononi/memo-Prodi02.doc".

[5] Upon Prodi's sudden fall in May 2008, Tononi in September the same year again appointed a Partner and Managing Director of the Investment Banking Division of Goldman Sachs, London.

On 15 September he has been appointed as President of bank Monte dei Paschi di Siena by the shareholders' meeting.