Former TD and Senator Ivor Callely has today been arrested by the Garda Fraud Squad.
The ex-Fianna Fáil representative, who resigned over an expenses scandal, is being questioned in relation to the mobile phone expenses he claimed during his time in the Seanad.
A Garda spokeswoman confirmed the former politician was detained just before lunchtime by the Garda Bureau of Fraud Investigation.
The 53-year-old was taken to Irishtown Garda station in Dublin for questioning.
He can be held for 24 hours under section four of the Criminal Justice Act.
Last April, a political ethics watchdog sent a file on Mr Callely to the Director of Public Prosecutions (DPP) after investigations into irregular communications claims.
The former senator was accused of falsely claiming about €3,000 for mobile expenses for a company that had gone out of business, leading to in-house probes and the Garda inquiry.
He is accused of supplying invoices from the business even though it was not trading.
It is understood the DPP will be examining whether a fraud has been committed.
Investigations were sparked in August 2010 when former Green Party backbencher Paul Gogarty made an official Garda complaint over reports that Mr Callely allegedly used invoices from a company that had gone out of business to claim mobile phone allowances.
The Standards in Public Office Commission (Sipo) examined the claims and filed a report.
Mr Callely was first embroiled in an expenses scandal after claiming allowances worth €81,000 for living in his holiday home in Kilcrohane, west Cork, over three years.
His political base was Clontarf, north Dublin, and a parliamentary investigation found he deliberately misrepresented his normal place of residence.
Mr Callely was handed a 20-day suspension from the Seanad which was subsequently overturned by the High Court after it ruled he had not been given the chance to defend himself.