The French Senate vice-president, Jean-Leonce Dupont, says the loss of parliamentary immunity means that French Polynesia's Gaston Flosse, can be detained at any time.
Mr Dupont says investigators into alleged corruption in the so-called OPT affair asked for the immunity to be lifted with the express purpose to have the powers to place the senator in detention.
The OPT probe centres on claims that Mr Flosse's party received kickbacks from a now detained French advertising executive, Hubert Haddad, for granting him public sector contracts.
The prosecutor in Papeete, Jose Thorel, has told local radio that a reason to jail the senator now would be to prevent him applying pressure to witnesses or other suspects or destroying evidence.
On two previous occasions this year, the French senate had rejected a request to lift Mr Flosse's parliamentary immunity.