The 64-year-old, who has remained a divisive figure since leaving power two years ago, will make a bid for a Senate seat in October's midterm elections, the reports said.

Cristina Kirchner took office in 2007, vowing to continue the work started by her husband Nestor Kirchner, who in 2003 inherited an economy in shambles after what was then the largest sovereign debt default in history.

Since leaving office Kirchner has channeled popular anger against the budget cuts of her successor Mauricio Macri, launching a new party called Citizen Union, and her return to politics spells a headache for the conservative president.

Kirchner is meanwhile being investigated over three sets of corruption charges and faces trial in a fourth case of alleged financial mismanagement as president.

She denies wrongdoing and says the cases are politically motivated.

A seat in the Senate would spare her jail if convicted. Her supporters hope it could also pave the way for a fresh presidential bid in 2019.