In his student years, he attended the Augustinianum College, where he met Romano Prodi and Giovanni Maria Flick.

On 24 June 1997, Treu, as Minister of Labour, proposed a delegated law, later named Pacchetto Treu, made with the intention of fight unemployment: with this law temporary agency work obtained legislative recognition from the Italian legal system.

[4] Once the political season of The Olive Tree ended, Treu occupied a marginal role in the Parliament, being however elected to the Senate in 2001 and in 2006 with The Daisy (La Margherita; DL) and in 2008 with the Democratic Party (PD).

In 2013, with the end of his parliamentary mandate, Treu became a member of the National Council for Economics and Labour, an assembly of experts that advises the Italian government, the Parliament and the regions, and promotes legislative initiatives on economic and social matters, and in 2017 he was named president of the assembly by the Gentiloni Cabinet, tough, on the occasion of the constitutional referendum of 2016, he voted to suppress it.

[5] In addition to this, in September 2014, Treu was named by the Renzi Cabinet as Special Commissioner of National Institute of Social Security (INPS),[6] until the election of Tito Boeri as president.