The director of Fine Gael's campaign to abolish the Seanad insists the public will save €20m a year by voting Yes.
However Richard Bruton said that the savings will not come immediately, because of the time it takes to redeploy the staff.
Oireachtas figures said the direct costs of the Seanad are around €8.3m, with the rest made up in staff supports and pension costs.
Minister Bruton is standing over the €20m figure.
"The only ones who can give costs are the Oireachtas commission and they are the ones who have given the €20m costs and they run the senate so they know what it costs," he said.
"That doesn't happen immediately because they go on a panel and get redeployed but those are genuine savings just the same as the immediate payments to the senators and their staff."