The newly-established Reform Alliance 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 says the campaign to date has been marked with cheap slogans.
She said the group made the decision after a meeting in recent days. The former Minister of State for European Affairs explained the decision to Lunchtime here on Newstalk.
The group has launched a Twitter account and also has a website listed. However Wicklow TD Billy Timmins has previously ruled out the formation of a new party.
However under reformed Dail rules, the group will get speaking time on some issues.
The members grouped together after being told they will not be allowed to run for Fine Gael in future because they voted against party policies.