He accused those who said he had revealed the probe of defamation.
Lotti, who is expected to survive the vote, voiced full confidence in the judiciary and said he was dealing with the probe with his “head held high".
He said the opponents of the ruling centre-left Democratic Party (PD) and its former leader, ex-premier Matteo Renzi, were using the probe "to strike at a political season".
"We won't let the Senate be used for media lynching," he added.
Lotti, Renzi's right-hand man, is facing a no-confidence motion over the CONSIP probe from the anti-establishment 5-Star Movement (M5S).
He is also facing a censure motion from a group that recently split from the PD, the small Democratic and Progressive Movement (MDP), which he referred to as "culturally subaltern and politically incorrect".
The MDP wants Lotti to be stripped of two of his three portfolios, for the publishing and media industry and for the interministerial economic planning committee (CIPE), leaving him with just the sports brief.
The MDP said it would not take part in the no-confidence vote.
Also involved in the CONSIP probe, for suspected influence-peddling, is Renzi's father Tiziano, who has stepped down as chief of his local PD chapter near Florence.
Renzi, former Florence mayor, quit as premier after losing a Constitutional reform referendum in December and as PD chief last month to trigger a party congress and his likely re-election.
Marroni, the CONSIP chief, says Lotti tipped him off on the probe, enabling him to get rid of listening devices from his office.
With ANSA
