Independent Senator David Norris has described the referendum to abolish the Seanad as a power grab by the Taoiseach.
Senator Norris said if the referendum is passed it will hand extraordinary powers to the government.
And he said it would be a dangerous move to scrap the Upper House.
It comes after the newly-established Reform Alliance said yesterday it is advocating a No vote in the referendum to abolish the Seanad.
The Fine Gael splinter group is calling for a rejection of the proposal because it says there has been insufficient debate on the plan.
Former Junior Minister Lucinda Creighton said the campaign to date has been marked with cheap slogans.