Fianna Fáil leader Micheál Martin has accused the Taoiseach of "a con job" for stating the abolition of the Seanad will save €20 million.
Speaking in the Dáil, Mr Martin said it was patently a "false truth" and the tactics used by Enda Kenny would "make Youth Defence and Libertas blush".
He asked the Taoiseach to withdraw the claim.
In response, the Taoiseach said he did not accept Mr Martin's assertion that it was a con job.
He said €20m is a statement of costs, indirect costs and pensions from the Oireachtas Commission.
Sinn Féin leader Gerry Adams asked why the issue of Seanad had not been dealt with by the Constitutional Convention.
He also asked what legal advice had been sought in regard to the conduct of officials in the Department of the Taoiseach regarding the referendum.
Mr Kenny said the issue of holding a referendum was contained in the Programme for Government.
He also said the Government is not running a campaign regarding the abolition of the Seanad.
Mr Kenny said officials had worked on the preparation of the legislation for the referendum.
The referendum on the abolition of the Seanad will take place on Friday 4 October.